
CcpigteM 



CQEXRiGHT DEPOSIXl 



NOTE 

In view of the discovery of tribiphenylmethyl 
while this book was in press, the statement on 
page 128 concerning the non-existence of sub- 
stances containing a single free bond is probably 
no longer true. 

The reader is also requested to substitute 
" alicyclic " for " allocyclic " wherever the latter 
form occurs in Chapter XVIII. 



OUTLINES OF 

ORGANIC CHEMISTRY 



A BOOK DESIGNED ESPECIALLY 

FOR THE 

GENERAL STUDENT 



BY 

F. J. MOORE, Ph.D. 

ASSOCIATE PROFESSOR OF ORGANIC CHEMISTRY IN THE 
MASSACHUSETTS INSTITUTE OF TECHNOLOGY 



FIRST EDITION 

FIRST THOUSAND 



NEW YORK 

JOHN WILEY & SONS 
London: CHAPMAN & HALL, Limited 

1910 






Copyright, 1910, 

BY 

F. J. MOORE 



Stanbope ipress 

H. GILSON COMPANY 
BOSTON. U.S.A. 



CCI.A261843 



PREFACE 

During the past few years, it has been one of the author's 
most agreeable duties at the Massachusetts Institute of Tech- 
nology, to deliver a course of about thirty lectures upon 
the underlying principles of Organic Chemistry. Those 
attending this course have been, almost exclusively, can- 
didates for the bachelor's degree in Physics, Biology and 
Sanitary Engineering. The experience thus gained has pro- 
duced the conviction that, for such students, a selection of 
topics is desirable which is somewhat different from that 
given to those who are fitting themselves to become or- 
ganic chemists, and consequently different from that outlined 
in most text-books designed for both classes of students. 

The material which has been found suitable for presenta- 
tion in these lectures is here put in book form, in the hope 
that it may prove useful to others who study Organic 
Chemistry from the non-professional point of view. 

In selecting from the vast number of organic substances 
those best adapted for study in a work of this kind, com- 
pounds have, as a rule, been included, either because they 
are themselves of practical importance, or because they serve 
as the most convenient examples for illustrating funda- 
mental principles which elucidate the chemical character of 
substances which are of practical importance. The word 
"practical" has been abused in so many ways, that some 
definition is desirable. For the purposes of this book those 
substances have been considered of practical importance 
which have a wide technical application, like acetylene 
or linseed oil; those which are important factors in vital 

iii 



iv PREFACE 

processes, like glycogen or urea; those which are familiar 
in the operations of daily life, like sugar or starch; or finally 
those which throw light upon some important theory. 
Theories and processes have been selected upon a similar basis. 
The attempt has been made to present these in a thoroughly 
scientific manner, no important subject being omitted merely 
on account of inherent difficulties of presentation or com- 
prehension. Numerous subjects of the greatest importance 
to the professional organic chemist have, however, been 
omitted without scruple, if their inclusion did not seem 
called for on the basis of the principle already laid down. 
The professional will look in vain for any mention of a sub- 
ject as important to him as the aceto-acetic ester synthesis 
or the Grignard reaction, and he will find no mention of the 
broad subject of cis-trans isomerism. Optical isomerism 
has, however, been dealt with in considerable detail, because 
so many important natural products are optically active. 
It has been the same in the matter of constitutional proof. 
All will agree that it serves no good purpose to present a 
constitutional formula unless it is at the same time made 
clear how such a formula serves as an epitome of the whole 
general chemical character and behavior of a compound. 
To give a rigid proof in the case of every substance men- 
tioned would, on the other hand, lead far beyond the limits 
of a book of this character. The attempt has been made to 
meet these difficulties in the following way: For simple 
and important compounds, well adapted for purposes of 
illustration, proof has been presented in considerable detail, 
in order that the student may clearly understand just what 
is meant by this important element in a chemist's work. 
With more complicated substances and derivatives, the 
chemistry of the compounds has usually been discussed with 
sufficient fullness to make the formula plausible. In some 
isolated cases the author must plead guilty to having presented 



PREFACE V 

formulae without any evidence at all. Where this has been 
done, it has been done as a choice of evils. In the case of 
such compounds as pinene, camphor, or uric acid, for exam- 
ple, it seems at least equally undesirable either to omit 
formulae altogether, or, on the other hand, to marshal for 
their support a host of unfamiliar and, for every other 
purpose, useless facts, each of which is as difficult to remem- 
ber as the formula it is intended to establish. The semi- 
philosophical question of the limit of information conveyed 
by a graphic formula and the validity of the valence theory 
are discussed in the last chapter as critically as seems ap- 
propriate in addressing non-professional students. The chap- 
ter which touches upon Physiological Chemistry stands, 
scientifically, upon a somewhat different footing from the 
rest of the book, but this difference has been perhaps suf- 
ficiently emphasized in the text. 

F. J. MOORE. 

MASSACHUSETTS INSTITUTE OF TECHNOLOGY, 

May, 1910. 



CONTENTS 



CHAPTER I. 

Introductory. 

page 
Fundamental Definitions. — The Purification of Organic Com- 
pounds. — Qualitative Analysis — Quantitative Analysis. — 
Calculation of the Empirical Formula. — Determination of 
the Molecular Weight. — The Graphic Formula 1 

CHAPTER II. 

The Saturated Aliphatic Hydrocarbons. 

Aliphatic and Aromatic Compounds. — Hydrocarbons of the Meth- 
ane Series — Substitution. — Nomenclature. — Petroleum. . . 34 

CHAPTER III. 

Alcohols and Their Derivatives. 
Alcohols. — Alkyl Halides. — Esters of Inorganic Acids 56 

CHAPTER IV. 

Acids and Their Derivatives. 

Acids. — The Acid Derivatives: — Chlorides. — Anhydrides. — 
Esters. — Amides 82 

CHAPTER V. 

Aldehydes, Ketones, and Amines. 

Aldehydes. — Ketones. — Chloroform and Iodoform. — Amines and 
Amides. — : Genetic Relationships between the Fatty Acids. 103 



Vlll CONTENTS 

CHAPTER VI. 

Unsaturated Compounds. 

page 
Ethylene. — Acetylene. — Unsaturated Acids 125 

CHAPTER VII. 
Polyatomic Alcohols and Their Derivatives. 

Glycols and Their Oxidation Products. — Dibasic Acids. — Tria- 
tomic Alcohols: Glycerin. — Industries Involving the Fats. — 
The Drying Oils 134 

CHAPTER VIII. 

Hydroxy-Acids. Optical Isomerism. 

Lactic Acid. — The Asymmetric Carbon Atom. — Enantiomorph- 
ism. — The Principle of Optical Superposition. — The Tartaric 
Acids. — The Splitting of Racemic Forms. 147 

CHAPTER IX. 
The Carbohydrates. 

The Monoses. — Fermentation. — The Bioses. — The Glucosides. — 
The Polyoses. — Starch and Cellulose. — Industrial Uses of 
Cellulose ! 161 

CHAPTER X. 

Derivatives of Cyanogen and Carbonic Acid. 

Cyanogen and Its Derivatives. — Carbonic Acid Derivatives. — 
Urea. — Uric Acid and Associated Substances. — Carbon 
Bisulphide 182 

CHAPTER XI. 
The Amino-Acids and Proteins. 193 

CHAPTER XII. 
Organic Chemistry of Certain Vital Processes. 204 



CONTENTS IX 

CHAPTER XIII. 
Benzene and Its Homologues. 

PAGE 

Benzene. — Characteristic Reactions of Aromatic Compounds. — 
The Homologues of Benzene. — Halogen Derivatives. — The 
Sulphonic Acids ." 218 

CHAPTER XIV. 

Aromatic Nitrogen Compounds. 

Nitro-Compounds. — The Aromatic Amines. — The Diazo-Reac- 
tion. — Constitution of the Diazonium Salts. — The Azo-Dyes. — 
Chromophore and Auxochrome Groups 240 

CHAPTER XV. 

Aromatic Oxygen Compounds. 

Phenols. — Aromatic Acids. — The Aldehydes. — The Ketones. — 
The Quinones 257 

CHAPTER XVI. 

Some Important Dyes. 

The Derivatives of Rosaniline. — The Phthaleins. — Indigo 270 

CHAPTER XVII. 
Naphthalene and Anthracene. The Coal-Tar Industry. 280 

CHAPTER XV7II. 
Heterocyclic and Allocyclic Compounds. 

Heterocyclic Aromatic Compounds. — The Alkaloids. — The 
Allocyclic Compounds. — The Terpenes and Camphor. — India 
Rubber 290 

CHAPTER XIX. 
The Structure Theory. 303 



OUTLINES OF 
ORGANIC CHEMISTRY. 



CHAPTER I. 

INTRODUCTORY. 

The division of the subject of Chemistry into two great 
fields called respectively Organic and Inorganic Chemistry , 
like all such classifications in science, is merely a matter of 
practical convenience. The distinction grew up historically 
from the tendency to classify substances according to their 
origin; thus those which were obtained directly or indi- 
rectly from plant or animal sources were ranked as organic, 
all others as inorganic. In the first class were placed 
such substances as sugar, alcohol, and acetic acid; in the 
second, those like salt, sulphur, or lead. In earlier times the 
distinction between these classes seemed more fundamental 
than at present, because as yet no process was known by 
which an organic compound could be prepared from an 
inorganic one, or built up from its constituent elements in 
the laboratory. Since such processes have been devised, 
and the synthetic method has assumed so much importance 
in the study of organic compounds, the arbitrary nature of 
the old classification has become more apparent. The old 
names have, however, been retained with a somewhat 
altered significance. We now define Organic Chemistry as 
that portion of the science which treats of the compounds of 
carbon. This element occurs so universally in substances 
of animal or vegetable origin that most compounds in- 

1 



2 OUTLINES OF ORGANIC CHEMISTRY 

eluded in the old classification are retained in the new, the 
subject-content of Organic Chemistry remaining much the 
same. 

Not only does the great number of the carbon compounds- 
— probably exceeding those formed by all the other ele- 
ments combined — justify the separate treatment of this 
important branch, but the methods of study show well- 
defined differences, both in mechanical technique and in 
theoretical point of view. It is, of course, true that the 
same laws govern chemical action in the one field as in the 
other. On the other hand, the every-day processes carried 
out in laboratory practice involve the habitual use of dif- 
ferent operations, and the theoretical considerations which 
govern the work are, as a general rule, quite different. 
For example, the fundamental theoretical conception which 
is constantly in the mind of the organic chemist in planning 
his researches is the valence theory. This has proved a 
far less serviceable guide in the inorganic field. 

Among those properties of organic compounds which 
are most likely to impress the beginner as differing from 
inorganic ones, the following may be mentioned as typical. 

1. Instability at High Temperature. While many 
inorganic compounds can be heated to incandescence with- 
out undergoing chemical change, nothing of the kind is to 
be observed among organic compounds. These, almost 
without exception, undergo decomposition by the time the 
temperature has been raised to dull redness, while a large 
proportion decompose at a much lower temperature. This 
decomposition by heat is usually accompanied by deposi- 
tion of free carbon, and this phenomenon, known as 
"charring," is therefore one of the most common analytical 
tests for the presence of "organic matter. 5 ' 

2. Solubility. We seldom have occasion to work with 
the more common inorganic compounds in any other than 



INTRODUCTORY 3 

aqueous solution; the majority of organic compounds, 
however, are practically insoluble in water, most of these 
being soluble to a greater or less extent in such media as 
alcohol, ether, acetone, chloroform, carbon bisulphide, and 
the like. Most of the reactions carried on in the organic 
laboratory take place to best advantage in such solvents. 
The. division of substances between two non-miscible sol- 
vents is also an operation frequently employed. 

3. Velocity of Reaction. Most of the inorganic com- 
pounds with which we are most familiar are electrolytes, 
that is, they are dissociated in aqueous solution into ions; 
hence the reactions which take place in such solutions are 
usually those between ions. As a result these reactions are 
practically instantaneous in character. The greater num- 
ber of organic compounds, on the contrary, are not electro- 
lytes, and the reactions between them, though often rapid, 
are frequently extremely slow, requiring hours, and some- 
times even days or weeks, for completion. As a result, the 
long digestion of reaction-mixtures at elevated tempera- 
tures is quite the rule in organic operations. 

It must be understood that no one of the distinctions 
which have been mentioned is in any sense absolute. 
Many organic compounds are electrolytes, many inorganic 
compounds are soluble in non-aqueous solvents, many 
reactions between organic substances take place with 
great velocity, and many inorganic substances decompose 
at no very high temperature. What has been said is only 
intended to show enough of the broad differences between 
the two subjects to justify an independent treatment. 
The name " Organic Chemistry" is also well justified, for 
although no one any longer believes that any mysterious 
"vital force" makes the operations of chemical affinity 
something different in the one class of compounds from 
what it is in the other, yet two things do remain true : first 



4 OUTLINES OF ORGANIC CHEMISTRY 

that, in practice, most organic compounds are still obtained 
directly or indirectly from organized bodies (animal or vege- 
table) and second, that the vital processes themselves are, 
as we shall see in more detail later, reactions between 
organic compounds. 

THE PURIFICATION OF ORGANIC COMPOUNDS. 

The fact that small amounts of impurities have a marked 
effect upon the physical properties, and sometimes upon 
the chemical behavior, of organic substances makes it im- 
perative, in most cases, that compounds be subjected to 
processes of purification before they can be analyzed or 
employed for synthetic operations. This makes it necessary 
to discuss those tests which may be looked upon as fur- 
nishing criteria of purity for an organic substance. Those 
most commonly employed are the determination of the 
melting point in the case of solids, and the boiling point in 
that of liquids. The knowledge of other physical constants 
such as the crystalline form, the specific gravity, the elec- 
tric conductivity, and the refractive index is also extremely 
useful either as means of identification or as furnishing 
tests for purity. These latter determinations are, however, 
much less frequently made in laboratory practice. 

To return to those first mentioned, a liquid is usually 
regarded as pure when its boiling point is constant, that is, 
when the whole of it will distill at a constant temperature. 
It should be stated at once that such a conclusion is not 
justifiable in all cases. Certain mixtures of liquids of defi- 
nite composition also distill at a constant temperature for 
a given pressure. In such a case, changing the pressure 
reveals the presence of a mixture of this kind, for then the 
boiling point will no longer remain constant. 

The boiling point of a liquid is usually obtained by distil- 
ling it ; — a process also very useful for purposes of purifiGa- 



INTRODUCTORY 5 

tion. The apparatus employed consists of a flask provided 
with a side neck which passes to a condenser. (Fig. 1.) 
Through the stopper of the flask is introduced a thermom- 
eter in such a way that the bulb comes just opposite the 




Fig. 1. 



opening of the side neck. It thus measures the tempera- 
ture of the vapors passing over. This gives the boiling 
point of the distillate at any given moment. It is fre- 
quently desirable to carry out a distillation under dimin- 
ished pressure — "distillation in vacuum" the operation is 
commonly called. For this purpose all joints in the ap- 
paratus are made air-tight, and the receiver is attached to 
some form of vacuum pump. A manometer is usually con- 
nected to the apparatus to indicate the pressure. 

The melting point of a solid is a characteristic property. 
A small amount of an impurity will frequently depress the 
melting point many degrees, so that in practice, when deal- 
ing with an unknown substance, processes of purification 
are repeated until the melting point of the material has 
reached a maximum. 



6 



OUTLINES OF ORGANIC CHEMISTRY 



The melting point of a solid is determined as follows: — a 
little of the finely powdered substance is introduced into a 
thin- walled tube closed at one end. (Fig. 2.) The tube 




Fig. 2. 



used should be about five centimeters long and one milli- 
meter in diameter. It is attached to a thermometer in such 
a way that the substance is just beside the bulb of the latter. 
Both are now heated slowly in a bath of some transparent 
liquid — usually concentrated sulphuric acid — until the sub- 
stance is seen to melt. The temperature is then read off on 
the thermometer. 

Solids are most frequently purified by crystallization. 
This operation is so constantly carried out in an organic 
laboratory that it should be described in some detail. The 
substance to be recrystallized is heated with such a quantity 



INTRODUCTORY 



^=M= 



of an appropriate solvent that the boiling solution is nearly 
saturated. The hot solution is rapidly filtered, in order to 
remove any insoluble impurities, and the filtrate is allowed 
to cool slowly. When cold the crystals which have been 
deposited are filtered off and washed with a little of the 
pure solvent. The adhering solvent is then removed as far 
as possible by suction, and the product finally dried, either 
by heat or by leaving it in a vacuum-desiccator (Fig. 3) which 
also contains some substance 
capable of absorbing the va- 
pors of the solvent. For 
this purpose concentrated sul- 
phuric acid is generally used, 
as it will absorb the vapors 
of water, alcohol, ether, and 
many other liquids. In carry- 
ing out the above operation, 
one of the most important 
things is the selection of a 
proper solvent. One should 
be used from which the solid 
will be deposited in well- 
formeds crystal easily washed. 




Fig. 3. 

In order to secure a good 
yield, it is also extremely desirable that the substance be 
but sparingly soluble in the cold solvent, but quite freely 
soluble at a higher temperature. In many cases, of course, 
these conditions can be but imperfectly realized. 

A problem frequently met with is the separation of two 
or more liquids which are miscible in all proportions, but 
which have different boiling points. If it does not so 
happen that the liquids form a mixture boiling at a con- 
stant temperature, it is possible to separate them by frac- 
tional distillation. When a mixture of water and methyl 
alcohol, for example, is boiled, the portion which first 



8 



OUTLINES OF ORGANIC CHEMISTRY 



volatilizes is relatively richer in alcohol than the liquid 
from which it distills. As the distillation proceeds, the 
percentage composition of the distillate progressively 
changes, so that the later portions contain relatively more 
water than the original mixture. If now, instead of col- 
lecting the whole distillate in one receiver, the receivers be 
changed repeatedly, a series of fractions will be obtained 
of varying concentrations. If each of these fractions be 
again distilled, further changes of concentration in the 
same sense take place, so that, by repeated distillations, it 




Fig. 4. 



is possible to effect a practically complete separation of the 
two components. 

Another operation of constant application is distillation 
with steam. (Fig. 4.) Many substances insoluble in water 
distill readily in a current of steam, although their own 
boiling points may be a hundred degrees or more higher 
than that of water. The process is chiefly employed for 
the purpose of removing from a reaction-mixture some 
one component which alone is volatile with steam. 



INTRODUCTORY 



Another operation which serves the same purpose depends 
upon the differing solubilities of substances in two liquids 
which are not miscible. If some substance, for example, is 
formed in an aqueous solution which is more soluble in 
ether than in water, its separation and purification may be 
effected by shaking the reaction mixture with ether. Later 
when the two layers have been allowed to separate, the sub- 
stance sought is found in the ethereal layer, whence it may 
be readily obtained by distilling off the ether. This opera- 
tion of " shaking out with ether" is of con- 
stant application, and is usually performed 
in a piece of apparatus called a "separatory 
funnel" (Fig. 5) which permits the lower 
layer of liquid to be drawn off through a 
stopcock at the bottom. Other liquids 
which do not mix with water may, of course, 
be substituted for the ether in special cases. 
Were any substance absolutely insoluble in 
one liquid and very soluble in another, it 
is clear that' all of the material might be 
obtained by one operation. As a rule, 
however, several treatments are necessary, 
because the conditions of solubility hinted 
at above are never realized in practice. 
The rule is that the concentrations of the Fig * 5 - 

solute in two non-miscible solvents is proportional to the 
solubilities of the dissolved substance in each solvent con- 
sidered separately. This ratio of solubilities is accordingly 
known as the " distribution coefficient." 




QUALITATIVE ANALYSIS. 



A complete system of analysis, such as we find in use for 
the study of inorganic substances, is at the present time 
lacking in Organic Chemistry. We have as yet no standard 



10 OUTLINES OF ORGANIC CHEMISTRY 

methods which can be relied upon to reveal all the compo- 
nents in any mixture of organic substances, and owing to 
the close resemblance which exists between the members of 
the various classes of organic compounds, and the multitude 
of classes which exist, it is probable that such a general sys- 
tem can only be developed in the distant future. It follows 
that for the present, when dealing with mixtures, special 
methods must be employed which are suitable to particular 
kinds of mixtures. When these are unfamiliar, new methods 
must be worked out by the experimenter. Such work re- 
quires a wide knowledge of Organic Chemistry, and there- 
fore cannot be discussed at all here. A practical problem 
which comes up constantly in organic work is the following: 
— Given a pure homogeneous organic compound, to detect 
the elements which it contains, and to determine the per- 
centage of each which is present. The processes involved 
in the solution of this problem are, in theory at least, 
extremely simple, and may well be taken up at this point. 
The opeiation, as a whole, is spoken of as the " elementary," 
or more frequently as the " ultimate," analysis of an organic 
compound. 

The elements which usually occur in organic compounds 
are comparatively few in number. The only ones which 
need to be considered here are carbon, hydrogen, oxygen, 
nitrogen, chlorine, bromine, iodine and sulphur. The vast 
majority of compounds contain no element outside of the 
first four in the list. 

To test for carbon, the substance is merely heated in a 
tube closed at one end. The presence of carbon is revealed 
by charring, with the simultaneous evolution of what is 
commonly called a " burnt odor." A few organic sub- 
stances are so volatile that they do not show this test well. 
In such cases it is necessary to completely oxidize the 
substance. This can usually be best effected by heating 



INTRODUCTORY 11 

with copper oxide. If carbon is present the gases evolved 
will then contain carbon dioxide, and this can be readily 
detected by the turbidity which it produces in lime water. 

A test for hydrogen is usually superfluous after having 
tested for carbon, since practically all organic compounds 
contain hydrogen. If any test is desired, the formation of 
water on heating or by combustion is sufficient. 

For combined oxygen, Chemistry still lacks any univer- 
sally applicable qualitative test, or any good general method 
for its quantitative determination. 

The other elements mentioned — that is, nitrogen, the 
halogens, and sulphur — are most conveniently detected after 
total decomposition of the organic material. For this pur- 
pose the substance is heated with metallic sodium in a small 
tube closed at one end, until decomposition has taken place, 
as witnessed by abundant charring. The tube is then 
broken under water, and the solution boiled and filtered. 

The chemical results of this operation may be summarized 
as follows : — Most of the carbon the substance contains is 
deposited directly as such. If nitrogen is also present, this 
combines with some of the carbon and some of the sodium 
to form sodium cyanide. Similarly, if the halogens and sul- 
phur are present, they unite with the sodium to form the 
corresponding binary compounds. Hence a solution pre- 
pared as above indicated would contain sodium cyanide if 
the substance analyzed contained nitrogen, sodium sulphide 
if it contained sulphur, and sodium chloride, bromide, or 
iodide, if these halogens were present in the original mate- 
rial. In this solution, then, which now contains no organic 
matter, the above anions may be tested for according to 
any of the methods commonly employed in the qualitative 
analysis of inorganic compounds. In order to test for the 
presence of a cyanide, for example, the alkaline solution is 
treated with a few drops of a solution containing iron in both 



12 OUTLINES OF ORGANIC CHEMISTRY 

the ferrous and ferric condition, and the mixture digested 
for a few minutes. Then upon acidification, a precipitate 
of Prussian blue results if nitrogen was originally present in 
the organic substance. 

6NaCN + FeS0 4 =Na 4 Fe(CN 6 ) + Na 2 S0 4 . 
FeCl 3 + 3NaOH = Fe(OH) 3 + 3NaCl. 
4Fe(OH) 3 + 3Na 4 Fe(CN) 6 + 12 HC1 

= 12NaCl + Fe 4 [Fe(CN) 6 ] 3 + 12H 2 0. 
Chlorides, bromides, and iodides may be recognized by the 
precipitates which they give with silver nitrate in dilute 
nitric acid solution. They may be further distinguished by 
the fact that chlorine-water liberates free bromine from 
bromides, 

Cl 2 + 2NaBr = 2NaCl + Br 2 , 

and free iodine from iodides. The former imparts a blood- 
red color to carbon bisulphide, the latter gives a violet 
color. 

If sulphides are present, they may be recognized by the 
black precipitates which they give with neutral silver nitrate 
or lead acetate: 

Na 2 S + PbAc~ 2 = 2NaAc~ + PbS. 
A more sensitive test, however, is that effected by adding a 
dilute solution of sodium nitroprusside, Na 2 (NO)Fe(CN) 5 . 
This reagent gives a violet color with soluble sulphides. 

When two or more of the elements just mentioned are 
present at the same time, the analysis is a little more com- 
plicated. Such cases are, however, rather the exception in 
practice. For dealing with them, the student is referred to 
any work upon Qualitative Analysis. 

QUANTITATIVE ANALYSIS. 

The principles involved in the quantitative determination 
of the elements in an organic compound are also extremely 
simple. The determination of carbon and hydrogen is 



INTRODUCTORY 15 

Now ^ of 0.12 is 0.0133, which is the weight of hydrogen in the water 

formed in the combustion. This hydrogen is, however, the same 

hydrogen which was originally in the substance used for the analysis. 

0133 
The percentage of hydrogen in the latter must therefore be ' or 

6.66. 

Similarly, the weight of carbon dioxide formed in the combustion 

is 0.2933 gram. The formula CO. shows that in carbon dioxide there 

are twelve parts by weight of carbon to thirty-two parts of oxygen, 

that is, the carbon constitutes \\ or T 3 r of the whole. T 8 r of 0.2933 is 

0799 
0.07999 gram carbon. Hence — — - — or 39.99 is the percentage of car- 

bon in the substance. 

The method most generally used for the determination of 
nitrogen in an organic compound is based upon principles 
entirely similar to those underlying that employed for the 
determination of carbon and hydrogen. In this case a 
difference of application is made necessary. The carbon as 
before is burned to carbon dioxide, and the hydrogen to 
water, while the nitrogen is liberated as such. This gas is 
collected and measured. It is therefore necessary that no 
other gases should be present which cannot be conveniently 
separated from nitrogen. In practice, the combustion is ac- 
complished entirely by means of copper oxide in an atmos- 
phere of carbon dioxide. A hard-glass tube is employed, 
sealed at one end. This has the same dimensions as that 
used for the determination of carbon and hydrogen. Next 
the closed end is first introduced some powdered magnesite 
or manganese carbonate, which will yield a steady stream of 
carbon dioxide when gently heated, MgC0 3 = MgO + C0 2 . 
Next to this comes some coarse copper oxide, then the sub- 
stance itself intimately mixed with fine copper oxide, then 
a long layer of coarse copper oxide and finally a spiral of 
freshly reduced metallic copper. The use of the latter will 
be explained a little farther om From the combustion tube, 
a small tube leads to a piece of apparatus called an azotom- 



16 



OUTLINES OF ORGANIC CHEMISTRY 



eter. This is shown in Fig. 7. It consists of an upright 
tube with a stopcock at the top, and, near the bottom, two 
side arms, by means of one of which it is connected to the 




Fig. 7. 



combustion tube. From the other, a long piece of rubber 
tubing leads to a leveling bulb. This serves to fill the ver- 
tical tube with a concentrated solution of potassium hydrox- 
ide as needed. At the beginning of the operation the 
upright tube is left nearly empty, the stopcock at the top 
being open. The combustion tube is now heated near the 
closed end until the air in the apparatus has been replaced 
by carbon dioxide. The leveling bulb is then raised till the 
vertical tube of the azotometer has been filled with potas- 
sium hydroxide solution, and the stopcock at the top is 
closed. The copper oxide at both ends of the combustion 
tube is next raised to a red heat, and finally the substance 
itself is subjected to this temperature. The nitrogen 



INTRODUCTORY 17 

evolved passes over into the azotometer, the accompanying 
carbon dioxide being absorbed by the solution of potassium 
hydroxide. It sometimes happens that substances con- 
taining nitrogen produce, on combustion, not only this gas, 
but also oxides of nitrogen. These are soluble in potassium 
hydroxide and some nitrogen would be lost in consequence, 
were it not for the presence of the hot spiral of reduced 
copper mentioned above. When oxides of nitrogen pass 
over this, the copper takes the oxygen, forming copper oxide 
while free nitrogen is liberated, 

2Cu + 2NO = 2CuO + N. 

It should be added that such a spiral of reduced copper 
must also be used in the determination of carbon and 
hydrogen whenever the substance to be analyzed contains 
nitrogen. The gas in the azotometer may be measured 
directly in that instrument or, better, transferred to a 
measuring tube over water. Its volume is reduced to 
standard conditions of temperature and pressure and the 
result multiplied by the weight of one cubic centimeter of 
nitrogen under those conditions. This gives the weight of 
nitrogen in the sample, from which the percentage may be 
calculated. 

To take a specific case, let it be supposed that 2 gram of an organic 
substance when treated as above yields 25.6 cubic centimeters of 
nitrogen at 20° and 782 millimeters pressure as observed by the barom- 
eter. This observed volume is reduced to standard conditions by 

means of the familar formula V = +0*00367 in which V o 

represents the volume the gas would occupy at 0° and 760 millimeters, 
v is the observed volume, t the observed temperature, and p the pressure. 
Here it has to be remembered that since the gas has been measured 
over water, the actual pressure under which it stands is equivalent to 
the atmospheric pressure as registered by the barometer minus the 
vapor tension of water at the prevailing temperature, in this case 782 
minus 17 or 765 millimeters. Having substituted these values in the 



IS OUTLINES OF ORGANIC CHEMISTRY 

formula, the result shows that the nitrogen present would occupy 24 
cubic centimeters at 0° and 760 millimeters. Under these conditions 
one cubic centimeter of nitrogen gas weighs 0.001254 gram. Twenty- 
four cubic centimeters will weigh 0.0301. Hence the percentage of 
nitrogen in the substance is 0.0301 -*- 0.2 or 15.05 %. 

When an organic compound contains one of the halogens 
or sulphur, their determination is effected by a method 
which also involves the complete oxidation of the carbon 
and hydrogen. In brief, this method consists in heating 
the substance in a sealed tube for several hours with fuming 
nitric acid at a temperature rather over 300°. By this 
treatment, complete oxidation of the organic material is 
effected, and any sulphur present is oxidized to sulphuric 
acid. The latter can now be determined in the usual way, 
by precipitation with barium chloride, forming insoluble 
barium sulphate. If the substance contains halogen it is 
customary to seal up with it in the tube an excess of solid 
silver nitrate. The chlorine, bromine, or iodine is then 
found as the corresponding insoluble silver halide when the 
tube is opened. This is filtered off and weighed, subject to 
the ordinary precautions observed in analytical work. As 
the percentage of halogen in the silver compounds, as well 
as that of sulphur in barium sulphate, is readily derived 
from their formula?, the calculation of the analyses offers 
no new difficulties and need not be further discussed here. 
For the complications which arise when two or more of the 
above elements are present at the same time, the student is 
referred to any work upon Quantitative Analysis. 

A determination of the oxygen in an organic compound is 
never made in practice, on account of the lack of any sat- 
isfactory method. Instead the percentage of oxygen is ob- 
tained by difference, the percentages of the other elements 
being added together and the sum deducted from 100 %. 
This practice has the serious objection, for one thing, that 



INTRODUCTORY 19 

all the errors of experiment made in the analysis are 
thrown upon the oxygen. It has also happened in serious 
scientific investigation that the presence of an element has 
been entirely overlooked because its atomic weight happened 
to be an even multiple of that of oxygen. 

CALCULATION OF THE EMPIRICAL FORMULA. 

Having obtained the percentages of the different ele- 
ments in an organic compound, the next step is to deter- 
mine from these data the empirical formula. This resembles 
in principle a problem in elementary arithmetic which may 
be stated thus : "In a pile of cannon balls weighing a 
hundred pounds, there are thirty pounds of ten-pounders, 
forty of five-pounders and thirty of two-pounders. How 
many of each kind of ball are there in the pile?" In 
this case the total weight of each kind of cannon ball is 
divided by the weight of one ball of that kind. Similarly, 
in the chemical problem, the weight of each element present 
is divided by the atomic weight of that element. There is 
this difference, however, in the two problems: the weights 
of the cannon balls are actual weights, while the atomic 
weights of the elements are relative quantities. The result- 
ing quotients, therefore, in the latter case cannot be the actual 
number of atoms present in the molecule of the compound 
but are simply quantities which stand to each other in the 
same ratio as those numbers. On this account it is just as 
well to divide the percentages of the elements by the atomic 
weights as to employ the actual weights, and in practice 
this is usually done. 

As a concrete example, the case of the compound whose 
analysis was given on page 15 may be cited. It will be 
recalled that the analysis showed 40 % carbon and 6.66 % 
hydrogen. The sum of these deducted from 100 % gives 
53.34 % oxygen. These percentages divided by the atomic 



20 OUTLINES OF ORGANIC CHEMISTRY 



weights of the respective elements yield quotients which 
stand to each other in the ratio of 1:2:1. 

C 40. 4- 12 = 3.33 

H 6.66 -T- 1 = 6.66 

O 53.34 - 16 = 3.33 



f 1 
I--S- 3.33 = h 

u 



100.00 

Hence it is obvious that a compound of the formula CH 2 
would satisfy all the conditions imposed by the analysis. 
It is clear that these would be equally well satisfied by 
the formula C 2 H 4 2 or C 3 H 6 3 . In fact, what the analysis 
of the compound has really given is the formula (CH 2 0) n , in 
which the value of n remains undetermined. This is as 
much as can be learned from the analysis alone. In order 
to fix the formula of the compound more definitely it is 
necessary to determine the molecular weight. To continue 
the illustration, a compound of the formula CH 2 must have 
the molecular weight 12 + 2 + 16 = 30. C 2 H 4 2 represents 
a molecular weight of 24 + 4 -f 32 = 60, similarly the 
formula C 3 H 6 3 corresponds to a weight of 90; and so on. 
It follows that if a molecular weight determination had 
yielded the value 60, the formula of the compound would 
be fixed as C 2 H 4 2 . This is spoken of as the empirical 
formula of the compound as distinguished from its graphic 
or constitutional formula. 

DETERMINATION OF THE MOLECULAR WEIGHT. 

It is fortunately possible to determine the molecular 
weight of a compound by methods which are based upon 
its physical properties and which are independent of the 
results of analysis. The method which is historically the 
most important, and may be considered the standard, is 
that based upon the determination of the vapor density. 
The only theoretical principle involved is the hypothesis of 
Avogadro, which states that, under the same conditions of 



INTRODUCTORY 21 

temperature and pressure, equal volumes of all gases con- 
tain the same number of molecules. For a full statement 
of the evidence upon which this important hypothesis is 
based, the student must be referred to works upon General 
and Physical Chemistry. Here a single fact will be recalled 
which has been verified by countless experiments, namely, 
that equal volumes of the more familiar gases have weights 
which stand to each other in the same ratio as those num- 
bers which, from analytical and other considerations, appear 
as the most probable molecular weights of the respective 
compounds. Thus two grams of hydrogen, thirty-two of 
oxygen, twenty-eight of nitrogen, seventeen of ammonia, 
and forty-four of carbon dioxide, when measured at 0° 
and 760 millimeters pressure, all occupy the same volume. 
This volume is called the molecular volume, and its numer- 
ical value is 22.4 liters, a number which it is worth while to 
remember. 

A mdej2ular__weight determination by the vapor density 
method consists in volatilizing a known weight of the sub- 
stance at a temperature well above its boiling point, and 
measuring the volume of the gas produced under the con- 
ditions of the experiment. From this weight and the 
volume observed (after applying the proper corrections for 
temperature and pressure) a simple proportion gives the 
weight of substance which, in the gaseous state, would 
occupy a volume of 22.4 liters, and this, as we have just 
seen, is the molecular weight. 

Returning to the case of the compound whose formula was derived 

on page 20, suppose that 0.1 gram of this substance, when volatilized, 

yields a volume of gas which, when reduced to 0° and 760 millimeters, 

would occupy 37.3 cubic centimeters. The proportion then holds: 

0.1 : 37.3 : : x : 22400. 

. 2240 ° m 
X== -37T =60 ' 

that is, sixty grams of the substance would occupy 22.4 liters, or 60 is 

the molecular weight of the compound. 



22 



OUTLINES OF ORGANIC CHEMISTRY 



4 D 



^mE 



The apparatus almost universally employed for the de- 
termination of the vapor density in practical organic work 
is that shown in Fig. 8. It consists of an oblong bulb of 
glass, of about 200 cubic centimeters 
capacity, which is prolonged up- 
ward into a stem about 60 centi- 
meters long. At the top of this 
stem are two side-arms, one of 
which passes under the water in the 
vessel E, while to the other is at- 
tached a short piece of rubber tubing 
through which passes a glass rod, 
in such a way that its inner end 
extends entirely across the upright 
stem of the apparatus at C. The 
larger bulb can be kept at a con- 
stant temperature by boiling some substance 
in the outer mantle A in such a way that 
its vapor will entirely surround the bulb B. 
For this purpose, a substance is usually 
selected whose boiling point is materially 
higher than that of the compound whose vapor 
density is to be determined. To carry out the 
operation, a suitable quantity of the substance 
to be investigated is weighed out into a small 
tube, and this is introduced into the top of 
the apparatus in such a way that it rests upon 
the glass rod at C. The top of the apparatus 
is then closed by a stopper, and heat is applied 
to the liquid in A until the whole apparatus 
has assumed a constant temperature. This is the case when 
no more air bubbles pass out through E. The measuring 
tube D is then filled with and water inverted over the 
outlet tube. At this point, the glass rod at C is sprung 




Fig. 8. 



INTRODUCTORY 23 

back, and the substance is allowed to fall into the bulb 
of the apparatus. Here it is at once volatilized, and displaces 
a quantity of air equivalent to that of its own vapor, 
the air being driven over into the measuring tube. In- 
asmuch as the air is cooled from the temperature of the 
bath to the temperature of the room in the course of 
the transfer, the quantity measured does not represent 
the volume which was occupied by the substance at the 
temperature of the bath, but instead, the volume which 
the vapor would have occupied, had it been possible for 
it to exist in the gaseous state at the temperature of the 
room. This is a great convenience in practice, for it removes 
the necessity of knowing the exact temperature of the bath, 
and when this temperature is extremely high, it is not always 
easy to measure. 

The result of the above experiment gives, then, the vol- 
ume which a given weight of substance would occupy in 
the gaseous state at the temperature of the laboratory. 
From this the molecular weight may be calculated accord- 
ing to the methods already indicated. It should be added 
that the experimental method above outlined is not the 
most accurate one by which such determinations can be 
made. It is, however, the most convenient; and for the 
purposes of the organic chemist, the highest accuracy is 
not essential in work of this kind. For example, in the 
case already so frequently employed as an illustration (see 
page 21) it is only desired to decide between the molecular 
weights, 30, 60, 90, etc., and it is clear that a method whose 
experimental error amounted to several units would still be 
sufficiently accurate for this purpose. 

It is obvious that vapor density determinations are only 
possible in the case of those substances which can be vapor- 
ized without decomposition. This applies to only a minor- 
ity of organic compounds. It is therefore fortunate that 



24 OUTLINES OF ORGANIC CHEMISTRY 

molecular weights of substances can be determined in solu- 
tion at lower temperatures. The fact that this is possible 
is due to certain analogies which exist between the gaseous 
state and the state of dissolved substances in solution. For 
a full account of these extremely important and interest- 
ing relations, the student must be referred to works upon 
Theoretical Chemistry. Here space only suffices for the state- 
ment of certain well-established facts which have a direct 
bearing upon the determination of molecular weights. 

It is well known that when a liquid contains another 
substance in solution, the freezing point of the solvent is 
thereby lowered; thus all know that salt water freezes at a 
lower temperature than fresh. What is, perhaps, not quite 
so familiar is the fact that, for dilute solutions at least, the 
depression thus caused is, for the same solute, proportional 
to the concentration of the solution, and, for different 
solutes, inversely proportional to their molecular weights. 
This is frequently stated in the form that equimolar solu- 
tions of different substances in the same solvent have the 
same freezing point. What is meant by the term " equi- 
molar " may, perhaps, be best illustrated by a specific ex- 
ample. The molecular weight of cane sugar is 342, of 
glycerin 92, and of glucose 180. Now if weights of the 
three substances be taken which are proportional respec- 
tively to these three numbers, and dissolved in three equal 
quantities of water, 1500 cubic centimeters, for example, 
then these three solutions will be equimolar, and will have 
the same freezing point, which will be lower than that of 
pure water. Had some other solvent been used instead of 
water, the same would have held true, that is, the freezing 
points of the three solutions would still have been equal. 
The depression of the freezing point caused in the two sol- 
vents would, however, have been different, this constant 
being dependent upon the nature of the solvent used. 



INTRODUCTORY 25 

In order to have some numerical system for recording 
this property of the various solvents, the molecular_jl£r 
p ression . of the freezing point has been defined as the num- 
ber of degrees which the freezing point of 100 grams of 
solvent is depressed by the addition of one mol (the molec- 
ular weight expressed in grams) of any solute. In the case 
of water, the numerical value of this constant is 18-5°. In 
the terms of the concrete example just mentioned, this 
means that the freezing point of 100 grams of water will be 
depressed 18.5° by dissolving in it 92 grams of glycerin, and 
that the same effect would be produced by adding, instead, 
180 grams of glucose or 342 of cane sugar. 

In practice, it is customary to work with far less concentrated 
solutions. Let it be supposed, for example, that 0.4 gram of an un- 
known substance, when dissolved in 25 grams of water, is found to 
depress the freezing point 0.2°. In the first place, it is obvious that a 
concentration of 0.4 gram in 25 is equivalent to 1.6 grams in 100. 
Since, now, 1.6 grams in 100 depress the freezing point 0.2°, while the 
molecular weight in grams dissolved in 100 grams of solvent depresses 
it 18.5°, the molecular weight may be readily found by the simple pro- 
portion, 

1.6 : 0.2 : : M : 18.5, 

from which M = 148. 

To put this in more general terms, if the weight of sample be desig- 
nated by g, the weight of solvent by s, the observed depression by d, 
and the molecular depression by D, then the molecular weight, M, 
may be found by the equation, 

s • d 

It should be stated that what has been said up to this 
point requires some qualification when applied to electro- 
lytes, that is, to those substances like acids, bases, and 
salts, which, notably in aqueous solution, undergo dissocia- 
tion into ions. Dissociation produces the same effect as 
the production of more molecules in the solution. The 



26 



OUTLINES OF ORGANIC CHEMISTRY 



results obtained by the above method are therefore not 
directly available for finding the molecular weights of elec- 
trolytes, unless they can be con- 
trolled by independent determi- 
nations of the degree of ionization. 
The apparatus employed for 
determining the molecular weights 
by the freezing-point method is 
shown in Fig. 9. It consists of a 
large test-tube A, into which dips 
a thermometer C. A is surrounded 
by a bath B, which is kept at a 
temperature slightly below that of 
the freezing point of the solvent 
used. Both vessels are provided 
with stirrers in order to maintain 
a uniform temperature. The ther- 
mometer used for this work is of 
special construction. It has an 
arbitrary scale so graduated that 
differences of temperature amount- 
ing to only T5oo° can be read from 
it. When a molecular weight is 
to be determined, a quantity of 
the solvent is weighed out into 
A, the temperature of the appa- 
ratus is lowered, and the freezing 
point of the pure solvent deter- 
mined. A weighed portion of the 
substance to be investigated is 
then added, and the freezing point 
again determined. The difference between the readings is 
the observed depression. All necessary data for the deter- 
mination of the molecular weight are now at hand. 




INTRODUCTORY 27 

It is a well-known fact that the presence of dissolved 
substances elevates the boiling point of a solvent as well as 
depresses its freezing point. This fact has also been made use 
of for the determination of molecular weights. The method 
needs no extended discussion here, however, for everything 
which has been said concerning the one property applies 
equally well to the other, and the apparatus used is con- 
structed in a manner entirely analogous. 

THE GRAPHIC FORMULA. 

In the preceding pages it has been shown how the empir- 
ical formula of a compound could be established from the 
results of a qualitative and quantitative analysis combined 
with a determination of the molecular weight. It might at 
first appear that when this had been accomplished the 
compound studied would have been thoroughly identified. 
In the case of organic compounds this is not so. In Inor- 
ganic Chemistry such formulae as H 2 0, NH 3 , and H 2 S0 4 
present to the mind certain definite compounds whose prop- 
erties are familiar. These formulae serve to thoroughly 
characterize the compound. How far this is from being 
the case in the organic field is best shown by stating the 
fact that for as simple a formula as C 4 H 6 3 there are 26 
compounds known to which it applies, and these compounds 
all differ among themselves in physical properties and 
chemical behavior. In the case of a formula no more com- 
plicated than C 10 H 16 it is found that no less than 157 exist- 
ing compounds are entitled to it. When, as in these cases, 
two or more substances have the same empirical formula they 
are called isomers, and the relationship itself is known as 
isomerism. It will be obvious that it would be highly de- 
sirable if formulae could be so written that a distinction 
might be drawn between these different isomers, for only 
in this way could serious confusion be avoided. It has been 



28 OUTLINES OF ORGANIC CHEMISTRY 

found possible to do this by making the fundamental 
assumption that the difference in properties exhibited by 
isomers — since it cannot rest upon any qualitative or quan- 
titative difference in their composition — must be due to 
a difference in the internal arrangement of the atoms within 
the molecules. Working upon this basis, it has proved pos- 
sible to formulate compounds in such a way as not only to 
distinguish the different isomers in a group, but also give a 
picture of the whole chemical character of the compound 
represented. Symbols of this kind are called graphic or con- 
stitutional formulae. By their aid it has been found possible 
to predict with considerable certainty the properties of com- 
pounds as yet unknown, and to devise methods for their 
actual preparation. 

Since both atoms and molecules are hypothetical in their 
nature it may well be asked how a knowledge of their 
arrangement is possible. An attempt will be made to deal 
with the general aspects of this question in the final chap- 
ter of the book, when the student has become acquainted with 
the use of graphic formulae and their interpretation, and is 
therefore better prepared than at present for a critical dis- 
cussion of this interesting subject. Here it is sufficient to 
state that the object of a graphic formula is not, essen- 
tially at least, to picture for us how the smallest particles 
of matter may be mechanically constructed, but rather to 
assist us in remembering, recording, and understanding the 
way in which chemical reactions take place between organic 
compounds. With this idea well fixed in mind, we may now 
pass over to a consideration of those fundamental assump- 
tions upon which constitutional formulae are based. These, 
on their face at least, suggest a highly mechanical concep- 
tion of the nature of matter. They are the Atomic Theory 
and the Valence Theory. Both of these are more or less 
familiar to the student of Inorganic Chemistry, but it will not 



INTRODUCTORY 29 

be out of place, for the purposes of the present application, to 
restate them briefly here. 

It is assumed by these theories that matter is made 
up of minute particles called molecules, these being the 
smallest units which can exist and yet retain the proper- 
ties of the substance of which they are components. It is 
further generally assumed that for a given substance the 
molecules are alike in mass and volume. The molecule, in 
its turn, is made up of atoms. These are extremely small 
portions of the elements which may be looked upon as the 
units of chemical combination. Like the molecule they 
are regarded as being, for a given element, of equal mass 
and volume. They are bound together by the force of 
chemical affinity, acting along or through the agency of 
certain points of union or attraction, whose number varies 
with the individual element, and which are variously known 
as " valencies," "bonds," "linkings," and the like. The 
atom, then, is to be thought of as a minute particle of 
matter — perhaps spherical — having upon its surface cer- 
tain points by means of which it may be attached to other 
atoms. The student may think of a kind of magnetic pole. 
This, however, is only an analogy, for the number is not 
limited to two as in the case of true magnets, nor has it 
been found possible to ascribe to certain ones a positive, and 
to others a negative polarity, though speculative attempts 
in this direction have been frequently made. 

The number of valencies which belong to each atom 
depends upon its nature and is determined in practice by 
a study of the composition of the more simple compounds 
which the element forms with other elements. Hydrogen 
is taken as the standard and to it is assigned the valence of 
one. Any other element of which one atom will unite with 
one atom of hydrogen to form a saturated compound is 
also given a valence of one. This is the case, for example, 



30 OUTLINES OF ORGANIC CHEMISTRY 

with the halogens which form with hydrogen the com- 
pounds, HC1, HBr, and HI. Those elements are said to 
have a valence of two, of which one atom unites with two 
atoms of hydrogen or of the halogens; thus we have the 
compounds, 

/CI 
H-0-HandCa( ' 

calcium and oxygen being bivalent. It follows that all 
valencies will be satisfied when one atom of a bivalent 
element unites with one of another bivalent element as in 
the compound, Ca = 0. Similarly a trivalent element is one 
whose atoms possess three points of attachment. Com- 
pounds will then be possible which contain one atom of a 
trivalent element to three of a monovalent element, — one 
atom each of two trivalent elements, — or three of a bivalent 
combined with two of a trivalent element. Thus nitrogen, 
boron, and aluminium are classified as trivalent elements, 
and we have such compounds as are represented by the 
following; formulas : 



i &= 



/H /C 1 A1 /0 



N-H, B = N, Al-Cl ")0. 

X H X C1, A1 n0 

Carbon is the most convenient example of an element with 
a valence of four, and this is perhaps best illustrated by the 
following formulas: 

7 h in .o ,h ^ 

c <h' c <h' c V c =°' C ^h" 

\ H Si X H 

It sometimes happens that, on account of the different 
compounds which it forms, an element must be assigned 
a variable valence. Nitrogen, for example, forms certain 
compounds in which it appears to have a valence of 



INTRODUCTORY 31 

five, whereas, in the majority of cases, as we have already 
seen, it is customary to ascribe to it a valence of three. 
Variable valence has been met with so constantly in Inor- 
ganic Chemistry that the whole valence theory has been 
thereby considerably weakened, and in that department of 
the science its usefulness has proved rather limited. In 
Organic Chemistry, on the other hand, we have, in practice, 
little to do with any other elements than carbon, hydrogen, 
oxygen, and nitrogen. The first three practically never 
show chemical behavior which suggests the possibility of 
variable valence, while in the case of nitrogen this occurs 
only in certain well-understood circumstances intimately as- 
sociated with the physical and chemical properties of the 
compounds involved. The student, therefore, has only to 
bear in mind that carbon has the valence four, hydrogen 
one, oxygen two, and nitrogen three and sometimes five. 
These four points well fixed in mind, in such a manner that 
they can be readily and constantly applied, will go far 
toward making the approach to the detailed study of 
Organic Chemistry an easy matter. 

Having said thus much about the atoms and the valen- 
cies, a word should be added concerning the way in which 
atomic arrangement is deduced from, or associated with, 
chemical behavior. Here, again, we are guided by assump- 
tions, which have, however, justified themselves in practice. 
The chief of these is that when in any chemical reaction an 
element or group is substituted by another, the substituting 
atom or group assumes the same position in the organic 
molecule which was originally occupied by that substituted. 
This may be illustrated by the following equation : 

H H H H 

II II 

H-C-C-OH + PC1 5 = H-C-C-C1+HC1 + P0C1 S . 
II II 

H H H H 



32 OUTLINES OF ORGANIC CHEMISTRY 

In this case oxygen and hydrogen leave an organic com- 
pound and chlorine enters it. If now the original com- 
pound had the constitution represented, the formula of the 
product is thereby determined, the chlorine being repre- 
sented as taking the place in the organic molecule which 
was vacated by the hydro xyl group. 

It is freely conceded that all these assumptions con- 
cerning the arrangement of hypothetical atoms in hypotheti- 
cal molecules are themselves highly hypothetical, and never 
have been, and perhaps never can be, susceptible of proof by 
direct observation. Considered, however, as a working hy- 
pothesis, the valence theory has proved one of the most fruitful 
in Natural Science. Historically, the whole subject of Organic 
Chemistry has been developed upon this basis, and the organic 
chemist habitually thinks in these terms. It is therefore 
essential that the student should, at the outset, familiarize 
himself with this point of view, and accustom himself, 
from the start, to associate every chemical reaction of an 
organic compound with its graphic formula. It may fur- 
ther be added that this method of study will be found an 
invaluable aid to the memory, and will make easy what 
might otherwise become a difficult subject. 

The student is particularly warned against attempting 
to memorize empirical formulae. This is a temptation 
under whose influence those unfamiliar with the subject 
are especially apt to fall. Empirical formulae have their 
uses for the professional as long as no others are available, 
but the beginner should pay them absolutely no attention what- 
ever. They are all so similar in form as to be practically impossi- 
ble to remember, and, as has already been pointed out, the 
same formula applies to so many different substances that 
it is ambiguous in meaning, and therefore, even if memo- 
rized, entirely useless to the student. When, for any rea- 
son, such formulae are desired, they can always be derived 



INTRODUCTORY 33 

at a moment's notice from the graphic formulae. The 
latter, because they take up more room, often appear more 
formidable to the beginner, but if he will, at the outset, 
learn to associate them with chemical behavior, he will be 
astonished to see how many will cling to his mind without 
effort. 



CHAPTER II. 

THE SATURATED ALIPHATIC HYDROCARBONS. 

Organic compounds are usually divided into two great 
classes, called respectively aliphatic and aromatic com- 
pounds. Unfortunately it is not possible to give any 
adequate definition of either of these words at this point. 
Both illustrate very well something which will frequently be 
found exemplified in the nomenclature of Organic Chem- 
istry. Certain groups of compounds or phenomena acquire 
names founded upon some outstanding characteristic, either 
of the group or of some prominent member. Later, with 
the rapid growth of the science, the name comes to be 
used in such a way as to include a much larger number 
of objects, and, on account of other characteristics which 
these possess, the name itself acquires a meaning quite 
foreign to its original one. For example, the word " aro- 
matic" was originally given to a group of compounds which 
possessed an odor to which this adjective might be appro- 
priately applied. Later, there came to be classed with 
these, on account of analogies in chemical behavior, other 
compounds which did not have this odor. Gradually the 
word " aromatic" became more associated with the chemi- 
cal properties of the larger group than with anything else, 
and it is only in this latter sense that it is now employed 
in Organic Chemistry. It is the same with the word, 
"aliphatic." This is derived from the Greek word, a\i<f>r), 
meaning "fat," and was originally applied to those sub- 
stances which were chemically closely allied to the fats. At 
the present time, however, although the fats are still classed 

34 



ALIPHATIC HYDROCARBONS 35 

among the aliphatic compounds, they can no longer be con- 
sidered as the most important members of the group, nor, 
indeed, as being typical, either in point of physical prop- 
erties or chemical behavior. In short, the names have be- 
come outgrown, and as they have remained in use, they 
have been forced to become conventional symbols for ideas 
not associated with their original significance. Something 
similar is, of course, to be met with almost everywhere in 
the history of words, but in the development of Organic 
Chemistry the changes of meaning have been more rapid, 
perhaps, than almost anywhere else. 

From what has been said, the student must not get the 
idea that such words as "aliphatic" and "aromatic" have 
become meaningless. On the contrary, they convey many 
ideas concerning chemical character and behavior which 
make them extremely useful and significant. These ideas 
cannot, however, be appropriately set forth in this place. 
Those substances first taken up in our detailed study will be 
aliphatic compounds. After the student has become familiar 
with the chemistry of these, he will have a better idea of 
the meaning of the adjective than could be derived from a 
definition. When the aromatic compounds come up for 
discussion, the more important differences between the 
classes will be dealt with. 

It is customary to begin the study of organic compounds 
with the hydrocarbons. This class derives its name from 
the fact that these substances contain only the two ele- 
ments carbon and hydrogen. Their structure is, in some re- 
spects, more simple than that of most of the other classes, 
and this makes it possible to regard them as types from 
which the other classes may be derived by substitution. On 
this account the hydrocarbons serve as the basis for a system 
of nomenclature. For these reasons it is appropriate that 
they be taken up at the beginning, although the establish- 



36 OUTLINES OF ORGANIC CHEMISTRY 

ment of their constitution may, at times, anticipate a slight 
knowledge of other classes not yet considered. 

There are several kinds of hydrocarbons. The only class 
which will be considered at present is the one which is 
named, from its simplest member, the methane series. It is 
also frequently called the paraffin series (from the Latin 
parum affinis — without affinity) . 

Methane, as shown by its density and the results of 
analysis, has the empirical formula CH 4 . When it is re- 
called that carbon shows the valence four and hydrogen 
one, it is evident that this compound is the simplest satu- 
rated one which could be formed by the two elements. Its 
constitution would therefore be appropriately expressed by 
the formula: 

H H 

1 y n 

H-C-H or C<„, 
H X H 

the direction assumed by the various valencies in space being 
considered, for the present, as a matter of indifference. 

Methane is also known under the name of " marsh gas" 
and, as this name indicates, it is sometimes formed by the 
slow decay of organic matter under water at the bottom 
of stagnant pools. It is also formed in large quantities in 
the distillation of coal. The gas whi;;h is manufactured in 
this manner for illuminating purposes contains on the aver- 
age about 35 % of methane, the other chief constituent 
being hydrogen. Since it is formed by the heating of coal, 
methane is naturally met with in coal mines, where it has 
received from the miners the name of "fire damp," on 
account of the serious explosions which take place when a 
mixture of the gas with air is accidentally ignited. 

Methane is one of the organic products formed when car- 



ALIPHATIC HYDROCARBONS 37 

bon is heated in an atmosphere of hydrogen at a temperature 
of 1200°, and this fact, while of no technical importance, 
is interesting because it shows how this simple hydrocarbon 
may be synthesized from its elements. As will be seen 
later, methane itself can be employed as a starting point in 
the synthesis of many other more complicated organic com- 
pounds. Other methods of formation, a little less direct, are 
the reduction of carbon monoxide by hydrogen in the pres- 
ence of metallic nickel: 

CO + 3H 2 = H 2 + CH 4 , 
and the reaction between hydrogen sulphide, carbon bisul- 
phide, and metallic copper at red heat: 

CS 2 + 2H 2 S + 8Cu = CH 4 + 4Cu 2 S . 
As carbon bisulphide and hydrogen sulphide can be obtained 
directly from the elements, this constitutes an indirect 
synthesis of methane. 

In the laboratory, met hane is u sually prepared b y heatin g 
sodium ace tate with soda-lirl!eT~ ^nagmucTi~as'this Inethod 
is very "generally applicable in similar cases, it should be 
given close attention. Acetic acid has the constitution, 

CH 3 

I 

c = o, 

\ 

OH 
as will be shown later, and if its sodium salt is heated with 
sodium hydroxide, sodium carbonate is formed and methane 
is evolved: 
H 
I 
H-C-H H 

I I 

C = O + NaOH = Na,CO, + H - C - H. 
\ I 

ONa H 



38 OUTLINES OF ORGANIC CHEMISTRY 

This is a perfectly general reaction; that is, it is almost always 
possible to prepare a hydrocarbon by heating with an alkali 
the salt of a certain acid containing one more atom of car- 
bon than the hydrocarbon sought. 

Methane is a colorless gas which can be condensed to a 
colorless liquid by cooling with liquid air at ordinary pres- 
sure. The liquid thus produced boils at — 164°. By evapo- 
rating it under diminished pressure, sufficient cold is produced 
to cause partial solidification. The gas burns with a scarcely 
luminous flame, and as has already been noted forms explo- 
sive mixtures with air and oxygen. 

Of the chemical properties of methane it may be said that, 
except for the. fact that it burns in air and oxygen, it is 
rather inert, being little affected by most ordinary reagents 
such as concentrated or dilute acids or alkalies. One reac- 
tion, however, is of all the more importance, namely, that 
which takes place with chlorine. The reaction is general 
and typical. In the dark, the gases react but slowly, while 
in sunlight the action may become so rapid as to produce 
explosion. The products formed are a mixture of hydro- 
chloric acid with a series of derivatives of methane which 
contain chlorine instead of hydrogen. The formation of 
these compounds may be represented by the following 
equations : 

H H 

I I 

(1) H-C - H + Cl 2 = HC1 + H - C - CI , 
I I 

H H 



/CI /CI 

(2) C<h + C1 2 = HC1 + C<§ 



ALIPHATIC HYDROCARBOXS 39 

/CI /CI 

n ' ci 

(3) C < jj + Cl 2 = HC1 + C <^j , 

X H X H 

.CI .CI 

(4) C <cf + Cl 2 = HC1 + C <£} • 

X H X C1 

These equations represent a type of reaction extremely 
common in Organic Chemistry. It is known as substitution. 
As was pointed out in the previous chapter, it is practi- 
cally always assumed in such cases that the substituent (in 
this case chlorine) takes the place just vacated by a hydro- 
gen atom in the organic molecule. It has already been 
pointed out that methane has the constitution, 

H 

I 

H-C-H, 

I 
H 

that is, that all of the hydrogen atoms are directly connected to 
carbon. It will therefore be well to remember that capacity 
for substitution by chlorine is a property quite generally 
found associated with hydrogen connected directly to carbon. 
A few of the properties of the compounds formed by the 
above reactions may profitably receive some attention at 
this time. The names, in particular, should be noted care- 
fully, as they illustrate principles constantly applied in 
organic nomenclature. The product of the first reaction 
is a methane in which one of the hydrogens has been replaced 
by chlorine. An appropriate name for the compound is, 
therefore, chlormethane. Another name which is more 
commonly used should also be mentioned. The combina- 



40 OUTLINES OF ORGANIC CHEMISTRY 

tion CH 3 (methane less one hydrogen) is a grouping of the 
elements which occurs very frequently in the formulae of 
organic compounds. It is, therefore, extremely convenient 
to have a name for this group. It is called methyl. Now the 
compound, 

H 

I 

H-C-Cl 

I 

H 

may be looked upon as a binary compound of the radicle 
methyl with chlorine. It is therefore called methyl chloride. 

At this point, the student makes his first acquaintance 
with a peculiarity of Organic Chemistry which he is to meet 
with constantly in his study of the subject, namely, that one 
and the same compound may have a number of different 
names which, if not all applied with equal frequency, are 
nevertheless all equally correct. The beginner is apt to 
look upon this as a difficulty and a stumbling-block. Even 
a limited acquaintance with the subject, however, soon con- 
vinces him that it is a matter of great convenience, as it 
helps him to look at chemical compounds from several points 
of view, each of which may be associated with a different 
name for the substance concerned, according to the particular 
relationship which it is desired to emphasize. It is believed 
that this will in general be found an aid to the memory 
rather than the reverse. 

Of the properties of methyl chloride, the only ones to 
which it is desired to call attention at this time are that it is 
a gas, and that its halogen atom is quite reactive, that is, 
it is subject to various metathetical reactions which will be 
studied more in detail later. Methyl chloride being a gas, 
it is not very convenient to work with, but the correspond- 
ing iodide, which is a liquid, finds constant application in. 



ALIPHATIC HYDROCARBONS 41 

every organic laboratory for the introduction of methyl 
groups into organic compounds. 

This compound is not prepared by the action of iodine 
upon methane, but from methyl alcohol by means of another 
method which cannot be profitably discussed at this point. 
It should, however, be stated that the hydrocarbons of the 
methane series may in general be substituted by the direct 
action of chlorine and bromine, while with iodine this is not 
practicable. 

The next product of the reaction of chlorine upon methane 

H' X C1 

may, in accordance with the principles already laid down, 
be called either dichlormethane or, more commonly, methyl- 
ene chloride, " methylene " being the name commonly used 
for the bivalent radicle, 

This word is, however, by no means so frequently met with 
as " methyl." Methylene chloride is a colorless oil boiling at 
40° and has no further interest for us here. 
The third product, 






might appropriately be called trichlormethane, but it is 
universally known as chloroform, a name given it before 
the valence theory was invented. The importance of this 



42 OUTLINES OF ORGANIC CHEMISTRY 

substance as an anaesthetic is familiar to all. Its properties 
and the technical method for its preparation will be dealt 
with later. 

The final product of the action of chlorine upon methane is 

Cl x /CI 

ci/ c \ci' 

carbon tetrachloride or tetrachlormethane, a methane in 
which all the hydrogens have been substituted by chlorine. 
It is a heavy oil boiling at 78.5° which is very useful as a 
solvent. 

None of these compounds is ever prepared technically 
in the manner indicated. The action of chlorine upon 
methane is too difficult to control, and leads to the for- 
mation of mixtures which are not easy to separate. The 
reaction is, however, of great theoretical importance, and 
the compounds formed have been mentioned here, partly 
because some of them are employed in reactions which we 
shall soon have occasion to study, and partly to illustrate 
two common methods of naming organic compounds. In 
accordance with the first, substitution products are named 
by prefixing to the name of the substance which serves as a 
type the name of the substituting atom or group. This is 
illustrated by the name " chlormethane." According to 
the second, the formula of the compound is divided, more or 
less arbitrarily, into radicles, and named as if the latter were 
its essential components. Thus the name " methyl chloride" 
would indicate that the compound it represents was a binary 
compound of the radicle methyl with chlorine. 

In addition to the names based upon chemical constitu- 
tion, there remain in use a large number of special names 
which were applied to well-known compounds before the 
introduction of the valence theory, and which it has not 
been found possible in practice to replace by more formal 



ALIPHATIC HYDROCARBONS 43 

scientific terms. These designations are usually referred to 
■ — not altogether appropriately — as " trivial names." 

Ethane. If one of the hydrogen atoms in the formula of 
methane be replaced by a methyl group or (what amounts 
to the same thing) if two methyl groups be written as directly 
joined together, jj jj 

I I 
H-C -C-H, 

I I 
H H 

the formula obtained is that of the next hydrocarbon in 
series, called ethane. 

One method for the preparation of this compound serves 
to establish the constitution which has just been suggested, 
for if methyl iodide be treated with zinc, a reaction takes 
place in the sense of the following equation: 

H H H H 

I I II 

H-C-!i+Zn + i:--C-H = ZnI 2 + H-C - C -H 

I I I I 

H H H H 

and ethane is formed. Of the properties of ethane little need 
be said which would not be a repetition of the most essential 
things which have been said concerning methane. This 
also is a gas which can be liquefied at a temperature of 4° 
under a pressure of forty-six atmospheres. It may be pre- 
pared by distilling sodium propionate with soda-lime, in a 
manner entirely analogous to the preparation of methane 
from sodium acetate. 

CH 3 

I 

CH 2 

I CH 3 

i'C = + NaO'iH = Na 2 C0 3 + | . 
' \ i CH 3 

ONa j 



44 OUTLINES OF ORGANIC CHEMISTRY 

When treated with chlorine, all of the hydrogen atoms may 
successively be substituted by that element. The products of 
this reaction need not be further discussed here except to note 
that, in names and properties, they are in every way analo- 
gous to the corresponding derivatives of methane. The first 
substitution product has the formula, 

H H 

I I 

H - C - C - CI, 

I I 
H H 

and is called ethyl chloride, ethyl being the name given to the 
important radicle, 

H H 

I I 

H-C-C- 

I I 

H H 

This stands in the same relation to ethane as methyl does 
to methane. Ethyl bromide and iodide are very important 
reagents in the laboratory. 

Up to this point, the term " methane series " has been 
employed several times without any definition being offered. 
A comparison of the compounds methane and ethane gives 
opportunity for a partial explanation. The formula of 
ethane may be derived from that of methane by substitut- 
ing one hydrogen atom in the latter by a methyl group. 
Two compounds whose formulae stand in the same relation 
to each other which that of ethane does to that of methane 
are called homologues, and a series of such compounds, in 
which the successive members stand in the same relation- 
ship, is spoken of as a homologous series. The student will 
become acquainted with many such series in the study of 
Organic Chemistry. The methane series, then, is made up 



ALIPHATIC HYDROCARBONS 45 

of all those compounds whose formulae may be derived from 
methane by the successive substitution of methyl for hydro- 
gen. A moment's thought will show that the number of 
members in such a series must be, theoretically at least, 
indefinitely large; and further, that since each member con- 
tains one carbon and two hydrogens more than the preceding, 
the empirical formula of any member of the methane series 
will correspond to the expression, C„H 2 „ + 2 , in which n repre- 
sents the number of carbon atoms! TrTe members of such 
homologous series strongly resemble each other both in 
physical properties and chemical behavior. This is a great 
convenience for the student, since it enables him to get a 
good idea of the chemistry of a whole series of compounds by 
the detailed study of a few members. It is too early to dis- 
cuss the various properties of homologous series in detail, 
but speaking generally it may be said that as the molecular 
weight increases, the compounds are found to have higher 
melting and boiling points and to be more inert in their 
chemical behavior. These statements require some quali- 
fication, but the more important exceptions will be touched 
upon later as examples arise. 

Propane. If one of the hydrogens in the formula of 
ethane be substituted by a methyl group, the formula of 
propane, the next member of the methane series, is obtained: 

H H H 

I I I 
H-C -C -C-H. 

I I I 
H H H 

This hydrocarbon may be prepared by heating sodium 
butyrate with soda-lime in a manner entirely analogous to 
that described already for the preparation of methane and 
ethane. It is gas at ordinary temperatures but is more 
readily condensed than the two substances just mentioned. 



46 OUTLINES OF ORGANIC CHEMISTRY 

To these it shows the closest analogy in all its properties, 
physical and chemical. 

An examination of the formula of propane shows that if 
one hydrogen be replaced by halogen the substitution can be 
made in two different ways, according as the hydrogen replaced 
belongs to a carbon atom at the end or in the middle of the 
chain. On making such a substitution there would result in 
the two cases the two following formulae, for the iodine com- 
pound for example: 



CH S CH. 

I I 

(1) CH 2 (2) C 



/H 



1 /H I Xl 

C(* 2 CH 3 

Now as a matter of fact there are two compounds known, 
both of which, as the analysis and molecular weight deter- 
minations show, have the empirical formula of an iodopro- 
pane, C 3 H 7 I. The student will recall that compounds thus 
related are called isomers, and since this is the first case of 
isomerism which he has thus far encountered, it will be well 
to take up at this point the nomenclature of isomers of this 
kind. The two compounds whose formulas have just been 
given are distinguished as "primary" and "secondary" 
propyl iodide, or perhaps more commonly as "normal"- and 
"iso "-propyl iodide. The meaning of these words should 
be made clear at once, as they are of constant occurrence in 
Organic Chemistry. A primary carbon atom may be defined 
as one which is directly attached to not more than one other 
carbon atom, and a secondary carbon atom is one which is 
directly attached to two others, while those linked to three 
and four others are called respectively tertiary and quater- 
nary. In the formula of propane the carbon atoms at the 
end of the chain are primary, the one in the middle is second- 



ALIPHATIC HYDROCARBONS 47 

ary. Turning to the formulae of the iodine substitution 
products, it will be seen that in (1) the iodine is attached to 
a primary, in (2) to a secondary carbon atom. This accounts 
for the names primary and secondary propyl iodide. 

As was pointed out above, the two compounds are also 
distinguished as normal propyl iodide and isopropyl iodide. 
In Organic Chemistry, the word " normal" indicates that 
the formula of a compound can be written in such a manner 
that all its carbon atoms shall form parts of one straight 
chain without arms or branches. The prefix " iso " is 
unfortunately less easy to define, because it has been applied 
rather indiscriminately to various compounds for which it 
has been found difficult to manufacture more logical names. 

The student now has the names and formula? of two more 
important radicles to remember. They are normal propyl, 

/ H 
H H C-H 

II / \ H 

H — C — C — , and isopropyl, — CH 

II \ / H 

H H C-H 

X H 

All that has thus far been said serves only to distinguish 
between the formulae of two possible compounds, C 3 H 7 L 
No answer has thus far been given to the more important 
question of which of the two formulae belongs to each of the 
two actual compounds. This has been satisfactorily decided, 
but the answer must be postponed until the corresponding 
alcohols have been taken up. In studying the next hydro- 
carbons of the series, the butanes, we shall meet with an 
instance of isomerism in which it will be possible to apply 
the formulae theoretically derived to the actual compounds 
at once. 

Before leaving the halogen derivatives of propane, it should 
be stated that propane is the highest member of the marsh 



48 OUTLINES OF ORGANIC CHEMISTRY 

gas series in which all the hydrogens can be directly substi- 
tuted by chlorine without causing a break in the carbon chain. 
When butane and its higher homologues are exhaustively 
chlorinated, the result is a mixture of varying proportions 
of tetrachlormethane, CC1 4 , and hexachlorethane, C 2 Cl fl . 

The Butanes. It has just been shown that one halogen 
atom can be substituted for hydrogen in the formula of 
propane in two different ways. The same holds true for the 
methyl group. This leads to the two following formulae: 

(1) CH 3 -CH 2 -CH 2 -CH 3 . (2) CB^-Ch' '. 

\Lti 3 

It is obvious that formula (1) is that of normal butane. The 
other containing the forked chain is that of isobutane. 
Further inspection of this formula shows it is that of a 
methane in which three of the hydrogens have been sub- 
stituted by methyl groups. This leads to the name tri- 
methylmethane. This latter method of naming hydrocar- 
bons should be carefully noted, for it is frequently used 
when dealing with complicated formulae. 

Turning now from the formulae to the compounds them- 
selves, it is found that there exist two hydrocarbons which 
have the empirical formula, C 4 H 10 . Both are gases which 
can readily be condensed. In one case the liquid thus formed 
boils at 1°, in the other at — 17°. The two liquids have dif- 
ferent specific gravities. It is necessary to decide which of 
the formulae discussed above applies to each of the hydro- 
carbons. This has been determined in the following way. 
If ethyl iodide be treated with zinc, zinc iodide is formed 
and that butane which boils at 1°. Now the only butane 
which can be formed by the reaction is the normal com- 
pound, as will be seen by inspection of the following equation : 

CH 3 - CH 2 - I + Zn + I - CH 2 - CH 3 = 

Znl 2 + CH 3 - CH 2 - CH 2 - CH 3 . 



ALIPHATIC HYDROCARBONS 49 

It follows that the butane which boils at 1° is the normal 
compound, while that which boils at — 17° must have the 
structure of trimethylmethane. The latter formula is also 
supported by positive evidence, the details of which it would 
not be profitable to introduce at this point. 

The kind of argument just employed may be regarded as 
typical of the manner in which the constitution of organic 
compounds is established in practice. As this is the first 
case of the kind which the student has met, it may be worth 
while to analyze the last equation a little more in detail. 
Ethyl iodide can only have the formula ascribed to it 
because whichever one of the hydrogens in ethane is sub- 
stituted by halogen, only one compound can result, the 
hydrogens in ethane being all exactly equivalent. When 
the iodine atoms are removed by the action of the zinc, the 
free ethyl groups thus formed unite by those bonds which 
formerly held the iodine atoms. The two ethyl groups thus 
formed can unite with each other in no other way than to 
produce a compound with a normal chain of carbon atoms. 

The Pentanes. The hydrocarbons of the methane series 
having the general formula C 5 H 12 are called pentanes. 
Three graphic formulae are possible on the basis of the valence 
theory, and there are three hydrocarbons actually known. 
By processes of reasoning and experiment analogous to 
those employed in determining the constitution of the two 
butanes, the possible formulae have been distributed among 
the pentanes as follows : — 

Normal pentane CH 3 — CH 2 — CH 2 — CH 2 — CH 3 boiling at 36°, 

CH 3 . 

Dimethylethylmethane CH 2 — CH 2 — CH 3 boiling at 30°, 

CH 3 

CH 3 . . CH 3 

Tetramethylmethane C boiling at 9°. 

CH 3 / \CH 3 



50 OUTLINES OF ORGANIC CHEMISTRY 

The Hexanes. For the formula, C 6 H 14 the theory ac- 
counts for the existence of five different compounds, and five 
hydrocarbons are known. These are distinguished as fol- 
lows : — 

Normal hexane CH S - CH 2 — CH 2 — CH 2 — CH 2 — CH 3 boiling at 69°, 

.CH.-CHg 
Methyldiethylmethane CH a — CET boiling at 64°, 

\CH 2 ~CH 3 

CH 3V 
Dimethylpropylmethane N CH — CH 2 — CH 2 — CH 3 boiling at 62°, 

CH 3 / 

GHg ^ . CM, 

Dimethylisopropylmethane CH — CH boiling at 58°, 

CH 3 / ^CH 3 

CH 3 v y CH 3 
Trimethylethylmethane C boiling at 49.6°. 

CH 3 / \CH 2 -CH 3 

This list is not given because of the intrinsic importance 
of the compounds themselves. They are, on the contrary, 
very unimportant, and the student could hardly make a 
worse use of his time than in memorizing these names and 
boiling points. On the other hand it would be an excellent 
exercise in the application of the valence theory for the 
student to write the graphic formulae of all the possible 
heptanes, C 7 H 16 , and to construct rational names for each. 

The value of the list is that it serves to illustrate several 
important properties of the methane series and of homologous 
series in general. As already indicated, it holds true for 
compounds of analogous constitution, — the normal hydro- 
carbons for example, — that the boiling points rise as the 
molecular weight increases. Among isomers the normal com- 
pounds have the highest boiling points, while those with the 
most forked chains, in general, have the lowest. Thus in 
the case of the hexanes, it will be noticed that the one 
with the lowest boiling point contains a quaternary carbon 



ALIPHATIC HYDROCARBONS 51 

atom, while the next lowest contains two tertiary carbons. 
It is generally true that those hydrocarbons which have 
the normal structure and those which contain quaternary 
carbon atoms are the most indifferent chemically, whereas 
the presence of a tertiary carbon atom seems to be asso- 
ciated with greater chemical reactivity. It will have been 
already noticed that the number of possible isomers increases 
rapidly with an increase in the number of carbon atoms. 
This is strikingly illustrated by the fact that for the general 
formula C 13 H 28 there are no less than 802 isomers theoret- 
ically possible. Not to discourage the beginner, it should 
be stated at once that only one is at present known. It is 
the same with most of the higher formula?. Chemists have 
not found it worth while to attempt the preparation of all 
these compounds, since their properties, as far as can be 
judged from analogy, would possess little individual interest. 
The methane series is not infinite in extent. The highest 
empirical formula belonging to the series which can boast an 
actual hydrocarbon to represent it is C 60 H 122 . The proper- 
ties of this compound, however, show nothing to lead us to 
suppose that still higher members might not be prepared. 
This substance, which is called hexacontane, is supposed to 
have the normal structure, though the proof is not quite 
complete. At all events the idea of a molecule containing 
sixty carbon atoms in a single chain furnishes food for reflec- 
tion, though speculations of this kind must be deferred for 
the present. 

Turning now to the physical properties of the compounds 
actually known, it will be seen by the list of boiling points 
already given that one of the pentanes, and all members of 
the series containing less than five atoms of carbon are gases 
at ordinary temperature. Those which contain from five to 
seventeen carbon atoms are liquids, while the normal hydro- 
carbons with more than seventeen atoms of carbon — and 



52 OUTLINES OF ORGANIC CHEMISTRY 

in the higher series the normal hydrocarbons are practically 
the only ones known — are solids. Ah are colorless when 
pure. They are lighter than water, the specific gravity 
of the solid and liquid members ranging from 0.45 to 0.78, 
and increasing slightly with the molecular weight. All are 
insoluble in water and more or less soluble in alcohol and 
ether. The different members of the series are miscible with 
each other, the liquids dissolving both the gases and the solids. 
Ordinary paraffin is a mixture of the higher solid members 
of the series, and its chemical inertness has extended the use 
of this name to cover the whole class. In spite of the name, 
there have been discovered in recent years quite a number 
of reactions in which these hydrocarbons take part, but it 
still holds true that they belong to the less reactive organic 
substances. The student will have an entirely adequate 
idea of their chemical behavior if he will recall that they 
are, for the most part, quite indifferent toward all reagents 
except chlorine and bromine. 

The names of the hydrocarbons of this series deserve a 
word of comment. After the first four members the names 
are derived from the Greek numerals. Thus there are hexane, 
heptane, octane, and so forth. The lower members of the 
series have names more or less arbitrary, which were origi- 
nally given them to indicate relationships which would now 
be considered rather remote. The student should fix these 
names, however, carefully in mind, because these, or such as 
are closely associated with them, are of constant occurrence. 
Thus there is associated with each of the hydrocarbons at 
least one monovalent radicle which stands in the same 
relation to the hydrocarbon that methyl does to methane. 
The names of this homologous series of radicles follow those 
of the hydrocarbons. The lower members are methyl, CH 3 ; 
ethyl, C 2 H 5 ; propyl, C 3 H 7 ; butyl, C 4 H 9 ; amyl, C 5 H n ; hexyl, 
C 6 H 13 , etc. The members of this series are spoken of collec- 



ALIPHATIC HYDROCARBONS 53 

lively as the alkyl radicles. The general formula of the alkyl 
radicles is C n H 2n + i- It is especially important that the 
student should have a perfectly clear idea of what is meant 
by the terms methyl, ethyl, propyl, and isopropyl. 

Occurrence. The petroleum found in Pennsylvania 
consists almost entirely of a mixture of the hydrocarbons of 
the methane series. These are also present in most other 
petroleums, but the Russian and Texas products contain, 
as well, hydrocarbons belonging to other series. Many pure 
hydrocarbons have been isolated from petroleum, but on 
account of the solubility of the various members in each 
other, and the well-known fact that many mixtures distill 
at a constant temperature, it is an extremely difficult opera- 
tion to secure material of which we can be sure that it 
represents a true chemical individual. For this reason, 
together with the general chemical indifference of the 
members of the methane series, petroleum has scarcely 
served at all as a starting point for the preparation of chemi- 
cal compounds. Instead, its components have been employed 
almost exclusively for purposes of heating and lighting, or as 
lubricants. For these uses the crude petroleum is dis- 
tilled and the various products washed with sulphuric acid 
and dilute alkali in order to remove basic and acid impuri- 
ties respectively. 

The various distillates have received different names 
according to their boiling points. It should be understood, 
however, at the outset, that these names do not indicate 
chemical individuals at all, but are commercial designations 
for material having boiling points which fall within certain 
limits. The material boiling between 50° and 60° and consist- 
ing mostly of pentanes and hexanes is called petroleum 
ether, that which boils between 70° and 90° is known as ben- 
zine or naphtha and that which boils between 90° and 120° as 
ligroin. The portion boiling between 150° and 300° is called 



54 OUTLINES OF ORGANIC CHEMISTRY 

kerosene, and this is perhaps industrially the most impor- 
tant product. Above 300° come various oils used as lubri- 
cants. By cooling these heavy oils paraffin may be made 
to crystallize out. The latter is used extensively in the 
preparation of candles. Paraffin is also obtained from the 
distillation of various other materials such as the boghead 
coals and the oil-bearing shales. When the heavier oils are 
heated to a temperature somewhat above their boiling point 
a peculiar action takes place which is technically known as 
" cracking." Chemically this consists cf a decomposition of 
the rather high members of the series in such a way that 
compounds of lower molecular weight are formed. 

Many theories have been advanced by scientists in order 
to account for the formation of petroleum in the earth. 
Those of the most importance are, first, that which ascribes 
the formation of petroleum to the distillation of vegetable 
material; second, that which ascribes it to the distillation of 
animal tissues, — probably of marine origin, — and, finally, 
what may be called the inorganic chemical theory, in accord- 
ance with which petroleum is formed by the action of water 
upon various metallic carbides. Some interesting argu- 
ments have been brought forward to support each of these 
theories, but as the question is by no means settled to uni- 
versal satisfaction, any discussion of the details would be 
out of place here. 

Constants which are considered of importance in dealing 
with oils are their specific gravity and flash-point. The latter 
is especially important in the case of illuminating oils, as 
it is essential that an oil should not be sold which is dan- 
gerous for use in lamps. The flash-point may be defined 
as the temperature at which the vapor of an oil forms 
an inflammable mixture with air. As determined in prac- 
tice, this is not to be considered as an accurate physical 
constant in the scientific sense, since the apparatus used for 



ALIPHATIC HYDROCARBONS 55 

the purpose is prescribed by law in the various states, and 
the method of making the determination is also prescribed. 
For this reason the flash-points determined in accordance 
with the differing specifications can hardly be expected to 
give concordant numerical results. The flash-point of an oil 
should, therefore, always be accompanied by a statement of 
the method by which it has been determined. 

In Massachusetts the apparatus employed consists of a glass cup set 
in a water bath of metal. In the oil cup hangs a thermometer. The 
cup is filled with oil to within ^ of an inch from its top, and the bath is 
heated by a flame | of an inch long at such a rate that the oil rises 2\° 
per minute till 97° F. is reached. After this, as often as the thermom- 
eter rises one degree, a small flame is passed across the rim of the cup. 
The temperature at which this operation first causes a transitory 
"flash" is taken as the flash-point of the oil. In Massachusetts, the 
law prescribes that an oil shall not be sold for illuminating purposes 
whose flash-point as determined by this method is lower than 100° F. 



CHAPTER III. 

ALCOHOLS AND THEIR DERIVATIVES. 

If an alkyl halide such as methyl iodide be treated with 
moist silver oxide, a reaction takes place in the sense of the 
following equation: 

H H 

I I 

2H - C - I + Ag,0 + H 2 = 2AgI + 2H-C -OH. 

I I 

H H 

The product may be looked upon as a binary compound of an 
alkyl radicle with the hydroxyl group, or as a hydrocarbon 
in which one of the hydrogens has been replaced by hydroxyl. 
Such substances are called alcohols. They form a homolo- 
gous series of which the simplest member is methyl alcohol, 
whose formula has just been given. This alcohol, and 
incidentally the methyl group as well, derives its name from 
the Greek words, pidv, wine, and v\yj, wood. It received 
this name (which finds an equivalent in our expression 
"wood spirit") from the fact that technically it is prepared 
by the distillation of wood. Several other important organic 
compounds are formed at the same time, and any descrip- 
tion of the details of the process and the purification of the 
methyl alcohol will best be postponed until the chemistry of 
these substances has received attention. 

Methyl Alcohol is a colorless liquid which is odorless when 
pure, but as ordinarily prepared it possesses a raw odor some- 
what resembling that of ordinary alcohol, and a sharp burn- 
ing taste. Under the influence of intense cold, it forms a 

56 



ALCOHOLS AND THEIR DERIVATIVES 57 

solid which melts at - 97°. Methyl alcohol boils at 64.5° 
and has a specific gravity of 0.812 at 0°. It burns with a 
blue smokeless flame and is miscible in all proportions with 
water. When such a mixture is saturated with solid potas- 
sium carbonate, the latter dissolves in the water while the 
methyl alcohol separates out as a layer upon the surface of 
the aqueous solution. In this way the alcohol may be 
separated from the water. The same thing may be effected 
with a considerable expenditure of time by fractional dis- 
tillation. In the arts methyl alcohol is used to a considerable 
extent as a solvent for gums, resins, and the like, as well as 
for fuel. In these ways it serves as a substitute for ordinary 
alcohol, and is also employed for denaturizing the latter. 
The two are similar in their physiological effect upon the 
organism, but methyl alcohol is much more poisonous. 

The chemical properties of this substance deserve careful 
study as they are typical of the behavior of a large and 
important class of substances. 

If methyl alcohol be treated with sodium, hydrogen is 
evolved and a substance is produced having the formula 
CH 3 — ONa. This is a methyl alcohol in which one hydro- 
gen atom has been replaced by sodium. It is called sodium 
methylate. If more sodium is employed than is called for 
by the equation 2CH 3 OH + Na 2 - H 2 + 2CH 3 ONa, no other 
product is formed. From this it may be concluded that 
methyl alcohol contains one, and only one, hydrogen which 
is replaceable by a metal. 

If methyl alcohol be treated with one of the halogen com- 
pounds of phosphorus, the pentachloride for example, the 
following reaction takes place: — 

CH 3 OH + PC1 5 = HC1 + POCI3 + CH3CI . 

The product is methyl chloride, with which the student is 
already familiar as one of the products of the action of 



58 OUTLINES OF ORGANIC CHEMISTRY 

chlorine upon methane (p. 39). The net result, then, 
of the action of phosphorus pentachloride upon methyl 
alcohol is the replacement of oxygen and hydrogen by a 
chlorine atom. 

We are now ready to discuss the constitution of methyl 
alcohol. In the first place, in accordance with the valence 
theory, if we accept the valence of four for carbon, two for 
oxygen, and one for hydrogen, no other formula than 

H 
I 
H - C - OH 

I 
H 

is possible for a substance of the composition of CH 4 0. It 
is, however, desirable to have some more positive argument, 
because the same reasoning could not be applied to the 
higher homologues of methyl alcohol. Fortunately such argu- 
ments are not lacking. It has already been shown that of 
the four hydrogen atoms, one can be replaced by sodium. 
From this it follows that one atom of hydrogen is combined 
differently from the other three. The formula given accounts 
for this fact by representing three of the hydrogen atoms as 
connected to carbon directly, while the fourth is connected to 
carbon through oxygen. When an alcohol is treated with 
phosphorus chloride, one oxygen and one hydrogen are 
eliminated while one atom of chlorine replaces both. This 
fact, that the oxygen and hydrogen go out together, may 
also be looked upon as entirely consistent with the assump- 
tion that the two are directly united in the molecule of 
methyl alcohol. This leads us to look upon this compound 
as made up of a methyl group combined with a hydro xyl 
group. In some of its reactions, this hydroxyl group shows 
some analogy with that of the inorganic bases. If methyl 
alcohol be treated with an acid, a reaction takes place which 



ALCOHOLS AND THEIR DERIVATIVES 59 

results in the elimination of water and the formation of a 
compound in which the methyl group is combined with the 
acid radicle. Such substances are called esters and their 
formation suggests the reaction of acids and bases to form 
salts : 

CH 3 (5H+ HNO3 = CH3NO3 + H 2 0. 
KOH + HNO3 = KNO3 + H 2 . 

The analogy is, however, almost entirely formal, for whereas 
acids and bases unite instantaneously and completely, the 
alcohols react with acids only slowly and incompletely. 
Furthermore the products are not salts at all but, for the 
most part, volatile substances insoluble in water and not 
electrolytes. Now the fact that their aqueous solutions 
conduct the electric current is one of the most characteristic 
things about salts. The student will therefore have a clearer 
idea of the chemical character of esters if he remembers the 
differences between them and salts rather than their points 
of resemblance. Because the alcohols react with acids in 
the manner just indicated it must by no means be concluded 
that they are bases, any more than, on the other hand, one 
would be justified in concluding that they were acids because 
they possess one hydrogen which may be replaced by a 
metal. Acids are electrolytes which yield hydrogen ions 
in aqueous solution, and the presence of these may be readily 
detected by their action upon indicators like litmus. Bases, 
in the same way, furnish hydroxyl ions which may be tested 
for in a similar manner. Alcohols, on the other hand, are 
neutral toward litmus and other indicators, and the reac- 
tions just learned are to be looked upon as characteristic 
of the hydroxyl group organically combined, and not of the 
hydroxyl ion. 

These reactions are so important that they may be profit- 
ably recapitulated. Alcohols have a hydrogen atom which 
may be replaced by metals like sodium and potassium. By 



60 OUTLINES OF ORGANIC CHEMISTRY 

the action of phosphorus halid.es the hydroxyl is replaced by 
halogen, and by the action of acids it is replaced by acid 
radicles. The student should associate this behavior with 
the presence in a compound of a hydroxyl group combined 
with an alkyl radicle. 

The behavior of methyl alcohol when treated with oxidiz- 
ing agents is also extremely important because a large class 
of alcohols, though not all, yield analogous products. 

If vapors of methyl alcohol mixed with air be passed over 
freshly heated platinum, oxidation takes place upon the 
surface of the latter with such velocity that it is kept glow- 
ing by the heat generated in the reaction. The chief product 
is a substance called formaldehyde, which has the formula, 

H 

I 

C = 0. 
I 
H 

This aldehyde, on further oxidation, yields a strong acid, 
formic acid, 

H 
I 

C = 0. 
\ 
OH 

The properties and constitutions of these substances will be 
treated in detail later. Here we are only concerned with 
the fact that methyl alcohol when treated with oxidizing 
agents yields first an aldehyde and then an acid, and that 
both the aldehyde and the acid contain the same number 
of carbon atoms as the original alcohol. 

Ethyl Alcohol, better known simply as " alcohol," is the 
next member of this homologous series. It is industrially 
by far the most important member of the entire group. 
It closely resembles methyl alcohol in all its physical and 






ALCOHOLS AND THEIR DERIVATIVES 61 

chemical properties. Thus it can be prepared from ethyl 
bromide by the action of moist silver oxide : 

H H H H 

II II 

2H-C-C-Br + Ag 2 + H 2 = 2AgBr + 2H-C-C-OH. 

II II 

H H H H 

Like methyl alcohol, it contains a hydrogen atom which can 
be replaced by sodium to form sodium ethylate : 

2C 2 H B OH + 2Na = H 2 + 2C 2 H 5 - ONa . 

The hydroxyl, too, may be replaced by halogen on treat- 
ment with one of the halogen compounds of phosphorus, 

3C 2 H 5 OH + PI 3 = 3C 2 H 5 I + P(OH) 3 . 

Finally, when it is oxidized, it yields 'an aldehyde, acetalde- 
hyde, of the formula; 

CH 3 - CH 3 

I * I 

C = O, and finally an acid, acetic acid, C = O , 

H OH 

both aldehyde and acid having the same number of carbon 
atoms as the original alcohol. 

Ethyl alcohol freezes at —117°, and boils at 78°. It is a 
colorless liquid of characteristic odor and burning taste. It 
is miscible in all proportions with water, and from such solu- 
tions it may be " salted out " by means of potassium car- 
bonate. A comparison of the above list with what has been 
said of the properties of methyl alcohol (page 57) may 
serve to give the student a good idea of the didactic advan- 
tages possessed by homologous series. 

Unlike methyl alcohol, the ethyl compound cannot be 
separated completely from an aqueous solution by fractional 
distillation. The two form a mixture of minimum constant 



62 OUTLINES OF ORGANIC CHEMISTRY 

boiling point which, at ordinary atmospheric pressure, con- 
tains about 95 % of alcohol. To remove the water from 
this mixture and obtain the so-called " absolute alcohol/ ' 
it is necessary to employ dehydrating agents. For this 
purpose, lime is most frequently used. The alcohol is boiled 
for some time with the lime, and finally distilled over it. 
If extremely dry alcohol is required, the product is finally 
distilled over small quantities of metallic sodium, or, perhaps 
better, over metallic calcium, which is now to be had quite 
cheaply in the market, and has the advantage over sodium 
that it does not so readily react with the alcohol. To test 
for the presence of water in alcohol, anhydrous copper 
sulphate is commonly added. After standing some time 
this turns blue if the alcohol contains water. Another test 
consists in the addition of calcium carbide, which evolves 
acetylene — easily recognized by its odor — when any water 
is present, but does not react with the alcohol. 

In mixtures of alcohol and water, such as distilled spirits, 
the proportion of the former is usually determined in prac- 
tice by taking the specific gravity of the liquid. Inasmuch, 
however, as alcohol and water unite with contraction of 
volume, tables are necessary in order to obtain the alcohol- 
content from the specific gravity. Special forms of hydrom- 
eters have been constructed with a stem so graduated 
that when immersed in a mixture of alcohol and water, the 
depth to which the apparatus sinks, shows directly the per- - 
centage of alcohol. Such instruments are called alcohol- 
ometers. If it is required to determine the alcohol in a 
mixture which, in addition to water, contains other substances 
which might affect the specific gravity, enough of the liquid 
is distilled to bring over into the distillate all of the alcohol. 
In this distillate the percentage of alcohol may now be 
determined by means of the specific gravity, and the result n» 
calculated over into terms of the whole quantity of liquid. 



ALCOHOLS AND THEIR DERIVATIVES 63 

This is the method employed for determining the alcohol con- 
tent of a wine or beer. It is obvious that if the mixture con- 
tains an appreciable quantity of other volatile constituents, 
the method cannot be employed. 

Industrial Preparation. Since prehistoric times alco- 
holic beverages have been prepared by the fermentation of 
sugars, and this method is still the only technical one for 
the production of alcohol. It is now known that this fermen- 
tation process is brought about by the presence in a dilute 
sugar solution of a substance called " zymase." Nothing 
is known of the constitution of this substance and very little 
about its chemical character. What is known is that it exists 
in yeast and some other organisms, and that its presence 
causes sugar to break up into alcohol and carbon dioxide in 
the sense of the following equation: 

C 6 H 12 6 = 2C 2 H 5 OH + 2C0 2 . 

Organic substances of this kind, which like zymase promote 
fermentation, are called enzymes. In practice, the source 
of the sugar used for these purposes is either the juice of 
fruits like the grape, or else the starch of grains or of the 
potato. In the latter case the starch is changed over to 
grape sugar by other enzymes before alcoholic fermenta- 
tion takes place. All this will be more intelligible when 
the chemistry of the sugars and starches has been studied. 
Here it is sufficient to note that when grape sugar is fer- 
mented by yeast, there results a mixture consisting chiefly 
of efchyl alcohol, but containing also a number of the higher 
alcohols. These are collectively known as " fusel oil," and 
recent investigations have made it highly probable that they 
owe their formation to the action of zymase upon the albu- 
minous material present rather than to any decomposition 
of the sugar. The purification of crude alcohol is a process 
of fractional distillation which is carried on with very com- 
plicated apparatus and on the largest scale. By this means 



64 OUTLINES OF ORGANIC CHEMISTRY 

there is obtained the alcohol of commerce. This is the 
mixture of alcohol and water of constant boiling point which 
has already been alluded to. It contains about 95 % of 
alcohol. 

Aside from the enormous consumption of alcohol in bev- 
erages, large amounts are employed in the arts. It is used 
to some extent as fuel (in explosion engines, for example) 
but perhaps chiefly as a solvent, particularly in the chemical 
industries and in compounding medical preparations. It is 
of interest to note that ethyl alcohol is of much wider occur- 
rence in nature than is commonly supposed. It has been 
shown to be present in small but recognizable quantities in 
the leaves of plants, in rain water, and in snow. 

Propyl Alcohols. In the formula of propane, a hydro- 
gen may be substituted by hydroxyl in either of two ways 
forming, respectively, 

H H H H H H 

III III 

(1) H-C-C-C-OH and (2) H-C-C-C-H. 
Ill III 

H H H H OHH 

In formula (1) the hydroxyl is attached directly to a primary 
carbon atom, that is, to one which is itself not attached to 
more than one other carbon atom. In (2), however, the 
hydroxyl is connected to a secondary carbon atom. The 
two formulae are therefore distinguished as those belonging 
to primary and to secondary propyl alcohols. Now two 
alcohols of the composition C 3 H 8 are known. One of them 
is formed in small quantities during alcoholic fermentation; 
the other is a laboratory product. The one found in fusel 
oil boils at 97° and has the specific gravity 0.804, while the 
other boils at 81° and has the specific gravity 0.789. Both 
of these substances show the reaction with sodium, with 
the chlorides of phosphorus, and with acids, which have 



ALCOHOLS AND THEIR DERIVATIVES 65 

just been described. This shows that they are both alcohols, 
that is, that they both contain the hydro xyl group. Since 
they are not identical, their differences must arise from a 
different position of the hydroxyl group. Such a difference 
of position is shown in the two formulae derived above. 
To determine, however, which formula belongs to which 
alcohol, it is necessary to study the oxidation products of 
each. The propyl alcohol which is found in fusel oil, when 
oxidized with such a reagent as chromic acid, behaves in 
the manner already described as characteristic of methyl 
and ethyl alcohols, that is, it yields first an aldehyde and 
then an acid, both of which contain the same number of 
carbon atoms as the original alcohol. The alcohol boiling 
at 81°, on the other hand, yields under similar circumstances 
a substance called acetone. When this is oxidized a mixture 
of acetic and carbonic acids is produced. Now since methyl 
and ethyl alcohols are typical primary .a.lfloho]s r i t follows 
that the propyl alcohol from fusel oil has the constitution 
of a primary alcohol (1); while the other, which behaves 
differently on oxidation, must be secondary propyl alcohol 
and have the formula (2). These distinctions are so im- 
portant, and the conclusions involved are so far-reaching, 
that it will repay us to enumerate the various products of 
oxidation at this time, despite the fact that it will be neces- 
sary to assume the validity of certain constitutional formulae 
for which complete proof can only be given later. 

Turning first to ethyl alcohol, its relation to the com- 
pounds which are formed from it by oxidation is shown 
by the following scheme: 

H H H H 

II I I 

H-C -C-OH > H-C-C =0 > H-C-C = 

II II II 

H H H H H 0-H 

Ethyl alcohol Acetaldehyde Acetic acid. 



66 OUTLINES OF ORGANIC CHEMISTRY 

This may be expressed in the following form: Under 
the influence of oxidizing agents like chromic acid, the 
hydroxyl group, OH, is changed to the carbonyl group 
I I 

CO, and this, in turn, to the carboxyl group, C = O . 
I \ 

OH 

Of these the former is characteristic of aldehydes and ketones, 
the latter of acids. It will be noticed that, taking these 
groups as a whole, carbonyl has a valence of two and car- 
boxyl a valence of one. For this reason the latter group 
can stand only at the end of a carbon chain. When we 
turn to the oxidation products of the propyl alcohols, we 
find that the primary compound is perfectly analogous in 
its behavior to ethyl alcohol. This is shown by the follow- 
ing scheme : 

CH 3 CH 3 CH 3 

I 1 I 

CH 2 > CH 2 > CH 2 

I 1 I 

CH 2 C = O C - O 

\ \ \ 

OH H OH 

Primary propyl alcohol Propionic aldehyde Propionic acid. 

It has already been stated that secondary propyl alcohol 
acts differently. Its behavior may be shown as follows : — 
CH 3 CH 3 CH 3 

I y H I I 

c; --* c=o — -> c=o + co 2 
i x oh | \ 

CH 3 CH 3 OH 

Secondary propyl alcohol Acetone Acetic and carbonic acida. 

It will be noticed here that the first product of oxidation 
is a substance which is isomeric with propionic aldehyde. 
It differs from that compound, however, by the position of 
its carbonyl group, for whereas in the aldehyde this is 



ALCOHOLS AND THEIR DERIVATIVES 67 

connected on one side to an alkyl radicle and on the other 
to hydrogen, in this compound the carbonyl group is at- 
tached to two alkyls.: . Such substances are called ketones. 
They may be distinguished from aldehydes by their behavior 
on oxidation , It has been shown that aldehydes yield acids 
containing the same number of carbon atoms as the aide 1 " 
hydes themselves. Ketones, on the contrary, yield mixtures 
of acids containing fewer carbon atoms than the ketones. 
This behavior finds complete expression in the graphic 
formula, for since a carboxyl group can exist only at the 
end of a chain, it is clear that a carbonyl group between two 
alkyls cannot be oxidized to carboxyl, unless its connection 
with one of the alkyls is broken. The latter itself then 
undergoes oxidation. 

As these two alcohols are types of important classes, it 
is worth while to recapitulate the distinctions between them 
in general terms. 

A^ primary alcohol, as defined according to its behavior, 
is one which, on oxidation, yields first an aldehyde and then 
an acid, both of which have the same number of carbon 
atoms "as the original alcohol. This behavior finds expression 
in a formula which represents a hydroxyl group attached 
to a primary carbon atom, that is, to one which is itself 
attached to not more than one other atom of carbon. It 
is clear that such a carbon atom must stand at the end of 
a carbon chain. 

A secondary alcohol is one which, on oxidation, yields first 
a ketone having the same number of carbon atoms as the 
alcohol, but this, on further oxidation, yields a mixture of 
acids each of which contains fewer carbon atoms than the 
ketone. Defined according to its formula, it is an alcohol 
whose hydroxyl is attached to a secondary carbon atom, that 
is, to one which is itself connected to two others. 

Neither of the propyl alcohols is of sufficient intrinsic 



68 OUTLINES OF ORGANIC CHEMISTRY 

importance to justify further description here. Before leav- 
ing the subject, however, the proof should be given for the 
constitution of the two propyl iodides which was postponed 
when these two substances were first mentioned on page 46. 
It is now obvious that the propyl iodide which can be prepared 
by the action of phosphorus and iodine upon primary propyl 
alcohol is the normal compound, while the substance which 
is formed by the same reaction from secondary propyl alcohol 
is isopropyl iodide. 

Butyl Alcohols. For the general formula, C 4 H 10 O, the 
valence theory contemplates the possibility of the existence 
of four isomeric alcohols. All are known. They are dis- 
tinguished as follows : — 

(1) Normal primary butyl alcohol CH 3 -CH 2 -CH 2 -CH 2 OH 
boiling at 117°. 

y CH 3 

(2) Normal secondary butyl alcohol CH 3 — CH 2 — CH 

boiling at 100°. 

CHo x 

(3) Isobutyl alcohol x CH-CH 2 OFI boiling at 107°. ' 

CH 3 V 

CH 3 x 

(4) Tertiary butyl alcohol CH 3 -C-OH boiling at 83°. 

ch/ 

The first three suggest nothing with which the student 
is not already familiar, and he should be able from the 
formula} to predict with a good deal of certainty much of 
their chemical behavior, including the formula} of all the 
oxidation products of each. The fourth formula suggests 
something new. The hydroxyl of this alcohol is connected 
to a carbon atom which is in turn united, to three other 
carbons. Such a compound is called a tertiary alcohol, 
and can be distinguished from the others by its behavior 
on oxidation. Inspection of the formula shows that the 



ALCOHOLS AND THEIR DERIVATIVES 69 

hydroxyl group of this alcohol cannot be oxidized to the 

I 
bivalent carbonyl radicle CO, unless at the same time at 

I 
least one of the bonds which unite the carbon atoms be broken. 
As a matter of fact, it is found that tertiary alcohols when 
vigorously oxidized yield a mixture of products, usually acids 
and ketones, all of which contain fewer carbon atoms than the 
original alcohol. In the case immediately under considera- 
tion, tertiary butyl alcohol yields acetone and carbonic acid. 
The oxidation products of acetone have already been men- 
tioned (page 66). 

Before leaving the discussion of the three classes of alco- 
hols it is worth while to point out that the primary alcohols 

are characterized by the grouping — C , the secondary by 

X OH 

TT 

C , and the tertiary by — C — OH. 

X X OH y 

The butyl alcohols are of little practical importance. 
Their formulae may, however, serve as material for illustrat- 
ing a method of nomenclature which has been found ex- 
tremely convenient in the case of the more complicated 
alcohols. It has already been shown that hydrocarbons 
which possess very complicated formulae can be appropri- 
ately named, by considering them as derivatives of methane. 
In the same way, alcohols may be looked upon as substitution 
products of methyl alcohol. For reasons of euphony, methyl 
alcohol then receives the name carbinol. Ethyl alcohol, 
when named in this way, would be called methyl carbinol. 
Similarly, the four butyl alcohols whose formulae have been 
given above would receive respectively the following names: 
(1), normal propyl carbinol; (2), methyl ethyl carbinol; (3), 
isopropyl carbinol; (4), trimethyl carbinol. 



70 OUTLINES OF ORGANIC CHEMISTRY 

Amyl Alcohols. For the formula C 5 H 12 0, eight alcohols 
are theoretically possible, and all of these are known. The 
names and formulae should be written by the student as an 
exercise. In the case of the amyl alcohols, a further diver- 
sity is introduced by the fact that secondary butyl carbinol 
of the formula 



■* 



CH 3 -CH 3X ,H, 

CH/ CH ~ C ^OH 



exists in two different forms which are alike in most of their 
properties, but differ in their action upon the plane of 
polarized light. One of them rotates this to the right, the 
other an equal amount to the left. The fundamental 
principles underlying this particular kind of isomerism will 
be discussed later, when we come to study lactic acid. For 
the present it is sufficient to note that the one which rotates 
the plane of polarized light to the left is one of the more 
important components of fusel oil. In this mixture it is 
accompanied by a still larger proportion of the isomeric 
isobutyl carbinol of the formula, 

°)CH-CH 2 -CH a OH. 

A mixture of these two alcohols constitutes the ordinary 
" amyl alcohol " of commerce. This is an oily liquid boiling 
at about 130°. It has a characteristic odor which in high 
dilution is not disagreeable, but when the vapors are inhaled 
in considerable quantity, they have a very irritating effect 
upon the mucous membrane. This amyl alcohol is used 
to a certain extent as a solvent for gums and resins and for 
gelatinizing nitrocellulose. It is also used somewhat in the 
preparation of esters and other chemical derivatives. It 
should be borne in mind that since the original amyl alcohol 
is a mixture, the same holds true of its chemical derivatives. 



ALCOHOLS AND THEIR DERIVATIVES 71 

We are now in a position to survey the homologous series 
of alcohols as a whole. In the first place the series has the 
general formula C n Ii 2n + 1 OH. So far as the relationship is 
concerned which exists between structure and molecular 
weight on the one hand, and physical and chemical properties 
on the other, much which was said concerning the methane 
series of hydrocarbons might be repeated unchanged here. 
The student will have already noticed, for example, that 
with increasing molecular weight the boiling points become 
higher, and also, that, among isomers, the alcohols of normal 
constitution have the highest boiling points. It is rather 
curious that the tertiary alcohols, which as a rule have the 
lowest boiling points, generally have the highest melting 
points. Thus tertiary butyl alcohol is solid at room tem- 
perature while all its isomers are liquids. The solubility 
in water decreases as we ascend the scale; thus normal 
propyl alcohol is miscible in all proportions with water, 
while twelve parts of the latter are required to dissolve 
normal butyl alcohol. A saturated aqueous solution of com- 
mercial amyl alcohol contains only about 3%. The chemical 
activity decreases as the molecular weight increases. The 
reason for this may be that as the carbon chains increase in 
length, the hydroxyl group becomes a more and more in- 
significant fraction of the whole molecule. Hence, in the 
higher members of the series, the hydrocarbon character 
comes to predominate. The same thing expresses itself in 
the physical properties. The highest members of the group 
are wax-like solids somewhat resembling paraffin. As the 
molecular weight increases, the numbeT of isomers theoretic- 
ally possible also increases enormously, but among the com- 
pounds of high molecular weight hardly any except the 
normal alcohols are known. These are chiefly found as esters 
of the fatty acids in the natural waxes. It is an interesting 
fact, which applies not only to the alcohols but also to 



72 OUTLINES OF ORGANIC CHEMISTRY 

most of the various series of aliphatic compounds, that, in 
the higher series, those compounds with normal structure are 
the ones found in nature. 



^ 



ALKYL HALIDES. 

While discussing the hydrocarbons and alcohols, we have 
frequently had occasion to refer to the alkyl halides, and at 
different points the student has already had opportunity 
to become acquainted with most of the methods of prepa- 
ration and chemical reactions of these substances. Those 
already mentioned may profitably be recapitulated at this 
point. 

When the hydrocarbons of the methane series are treated 
directly with chlorine or bromine, substitution takes place 
with the formation of an alkyl halide (page 38) : 
C 2 H 6 + Cl 2 = HC1 + C 2 H 5 C1. 

It is characteristic of alcohols that they react with the 
halogen compounds of phosphorus in the sense of the fol- 
lowing equation: 

C 2 H 5 OH + PC1 5 = HC1 + POCI3 + C 2 H 5 C1. 

Finally it has been shown that the alcohols unite with 
acids to form products called esters, water being eliminated. 
This reaction holds true also of the halogen acids : 
C 2 H 5 OH + HC1 = C 2 H 5 C1 + H 2 0. 

Some of the reactions of the alkyl halides are also familiar. 
Thus the student has already learned that the alcohols may 
be prepared from the alkyl halides by the action of moist 
silver oxide : 

2C 2 H 5 I + Ag 2 % H 2 = 2C 2 H 5 OH + 2AgI, 

and when these compounds are treated with metals like zinc 
or sodium, the halogen is removed by the metal and a synthe- 
sis takes place : 

2C 2 H,I + Zn - Znl 3 + C 4 H 10 . 



ALCOHOLS AND THEIR DERIVATIVES 73 

Furthermore the alkyl halides take part in many meta- 
thetical reactions in which they usually serve to combine 
an alkyl group with some other organic radicle. Most 
of these reactions will best be considered separately as they 
arise, but one of the more important which may serve as 
a type is the following : 

C 2 H 5 Br + KCN = KBr + C 2 H 5 CN. 

The way in which the alkyl halides are related to other 
classes is well indicated by the following scheme, in which 
the ethyl compound is taken as an example, and the halogen 
atom is represented by the symbol X: 

CH 3 — CH 3 . ^H 3 — CH 2 — CH 2 — CH 3 

Ethane ^"\~V £/ Normal Butane 



CH 3 — CH 2 X. 

i * Ethyl Halide 

CH 3 -CH 2 OH/^^P CH 3 -CH 2 -CN 

Ethyl Alcohol *^£&* Ethyl Cyanide 




The student is strongly advised to prepare charts of this 
kind for himself in dealing with the various classes of com- 
pounds which he will have occasion to study. They are of 
great assistance in keeping in mind the genetic relationships 
which exist between the different classes of substances. 

The number of halogen compounds known is very large. 
Including the fluorine compounds, they comprise four homolo- 
gous series having the general formula C n H 2n+1 X. In the- 
ory there would be as many compounds possible in each 
series as in the case of the alcohols. There is no occasion 
for describing any considerable number of these substances 
in this place. Those which are most familiar because of 
their frequent use as reagents are ethyl bromide, the io- 
dides of methyl and ethyl, and those of the two propyls. 
These are volatile liquids, colorless when pure, of ethereal 



7 



74 OUTLINES OF ORGANIC CHEMISTRY 

odor and heavier than water, the specific gravity being 
roughly proportional to the amount of halogen which they 
contain. In laboratory practice the bromides are usually 
prepared from the alcohols by the action of potassium bro- 
mide and sulphuric acid. The iodides are prepared from 
the same source by treatment with phosphorus and iodine. 
Ethyl bromide boils at 38°, methyl iodide at 45°, and ethyl 
iodide at 72°. The specific gravities of these substances are 
1.468, 2.293, and 1.949, respectively. 

An important difference has to be noted between the 
alkyl halides on the one hand, and the inorganic compounds 
of analogous formula such as sodium or potassium chlorides 
on the other. The latter are soluble in water and are elec- 
trolytes. So far as the halogen is concerned, almost all act 
alike in aqueous solution, because under these circumstances 
they all furnish the common halogen ion. The inorganic 
chlorides, for example, give with silver nitrate a precipitate 
of silver chloride. With the alkyl halides it is different. 
These are sparingly soluble in water, their solutions are not 
conductors, and their behavior with such reagents as silver 
nitrate is not uniform but varies from compound to com- 
pound. Ethyl iodide reacts with this reagent almost in- 
stantly, the bromide after standing for some time, and the 
chloride not at all, even after continued heating. 

The Cyanides. The radicle cyanogen is closely allied 
to the halogens in many of its reactions, and this makes it 
appropriate to take up at this time the study of the impor- 
tant organic compounds which may be looked upon as alkyl 
derivatives of hydrocyanic acid. The cyanogen group can 
be combined with methyl for example, in one of two ways, 
to form compounds of the formulae CH 3 — C = N and CH 3 — 
N = C respectively. As a matter of fact, two compounds 
of this composition are known. One of these is formed 
when methyl iodide is allowed to react with potassium 



ALCOHOLS AND THEIR DERIVATIVES 75 

cyanide, the other when the same reagent is treated with 
silver cyanide. The two substances differ widely in their 
properties, and notably in their behavior toward hydrolytic 
agents like acids and alkalies. Under these circumstances 
the substance formed by the action of methyl iodide upon 
potassium cyanide reacts in the sense of the following 
equation : <S ^^ 5L ' 

(1) CH 3 -C = N + 2H 2 = CH 3 - c( QH + NH 3 . 

The other product, however, reacts as follows: 

(2) CH 3 -N=C + 2H 2 = CH 3 - NH 2 + HC^ 

It is not intended to take up the study of the products 
of these reactions at this point. Attention is simply called 
to one fact which is apparent from the equations them- 
selves. In (1) the organic product on the right-hand side 
has the same number of carbon atoms as the original cyano- 
gen compound; that is, the carbon atoms have remained 
together. In equation (2) they have been separated. 
This is regarded as evidence that the cyanogen derivative 
in the first equation has its two carbon atoms directly 
united, while in the second case the carbons must have been 
connected by means of the nitrogen. This constitutes proof 
for the formulae assigned to the two compounds in the 
equations as written. 

Those substances of which CH 3 NC is a type have hardly 
enough importance to warrant further attention here. 
Methyl cyanide, CH 3 CN, and its homologues are, on the other 
hand, extremely important. As is shown by equation (1) 
itself, these compounds are closely related to the acids. 
On treatment with hydrolyzing agents, they yield acids 
containing the same number of carbon atoms as the cyanides 



76 OUTLINES OF ORGANIC CHEMISTRY 

themselves; that is, the cyanogen group is changed to car- 
boxyl. In synthetic organic work this is one of the more 
common ways of preparing acids. This accounts for an- 
other name frequently given these substances. They are called 
acid nitriles, and the individual members are named from 
the acid which is formed by hydrolysis. Methyl cyanide, 
for example, is also called acetonitrile. These substances 
will again be referred to when the study of the acids and 
their derivatives is taken up in detail. Here it is suffi- 
cient to add that in physical properties they are quite com- 
parable to the alkyl halides and esters. Methyl cyanide is a 
colorless liquid boiling at 81° and having the specific grav- 
ity, 0.805. Ethyl cyanide boils at 98° and has the specific 
gravity 0.801. The solubility of these substances in water 
resembles that of the alcohols. The lower members of the 
series dissolve, but can be salted out by means of potassium 
carbonate. The higher members are insoluble. 

ESTERS OF INORGANIC ACIDS. 

It has already been shown that the alkyl halides are 
formed when the corresponding alcohols are treated with 
the halogen acids: 

C 2 H 5 OH + HBr <=> C 2 H 5 Br + H 2 0. 

This means that these compounds may be considered as 
esters of such acids. Now since some of the other esters 
of the inorganic acids have an importance as reagents scarcely 
inferior to that of the halides, a few of them will be men- 
tioned at this time, although the esters of the organic acids 
will not be taken up until the acids themselves have been 
discussed. Esters may be defined as those substances 
which are formed by the union -of alcohols and acids with 
elimination of water. The process is called ester ification. 
The products are, for the most part, volatile substances of 



ALCOHOLS AND THEIR DERIVATIVES 77 

ethereal odor, soluble with difficulty in water, and non-con- 
ductors of the electric current. The most characteristic 
thing in their behavior is the fact that by hg ating with w ater 
under pressure, orj riore readil y in the pr esence of al kalies 
and" acfcTs7~tney are again decomposed into the acids and 
alcohols from which they were formed. This process is 
called saponification. It follows from what has been said 
that the equation written above represents a typical rever- 
sible reaction, and consequently, in actual practice, can 
never go to completion in either direction. Instead an 
equilibrium., is reached when the velocities of esterification 
and saponification are equal. Thisis an extremely interest- 
ing application of the law of chemical mass action. The 
conditions which obtain will be considered more fully when 
we come to take up the preparation of ethyl acetate, a re- 
action which has been thoroughly studied quantitatively. 
Here it is sufficient to note that, in practice, when it is desired 
to prepare an ester by this method, it is necessary, in order 
to obtain a maximum yield, to remove the water formed 
in the reaction, so as to reduce to a minimum the splitting 
action of the water upon the ester formed. This is usually 
accomplished by the addition of dehydrating agents such 
as concentrated sulphuric acid. On the other, hand, when 
the object is to decompose _an, ester (saponification), it is 
customary to work in alkaline solution, in order that the 
acid formed may be neutralized, and hence removed from 
the reaction as soon as it is formed. The word " saponifica- 
tion" deserves a word of explanation. It literally means 
" the making of soap." As a matter of fact that technical 
operation is a chemical process of just this kind, and hence 
the word has gradually come to cover the whole class of 
chemical reactions of this type, so that it is now used in 
Organic Chemistry practically as a synonym of hydrolysis. 
One of the more important esters of this class is ethyl sul- 



78 OUTLINES OF ORGANIC CHEMISTRY 

phuric acid. It is formed when concentrated sulphuric acid 
is warmed with ethyl alcohol: 

C A OH + ^)S0 2 = H 2 + CA -°)S0 2 . 

The resulting mixture contains the organic product mixed 
with a large excess of sulphuric acid. For purposes of 
separation, the mixture is diluted and treated with solid 
calcium carbonate. This forms insoluble calcium sulphate 
and leaves in solution the soluble calcium salt of ethyl sul-' 
phuric acid. When the filtered solution is evaporated, this 
calcium salt crystallizes out, and now may be dried and 
weighed. It is again put into solution, and decomposed 
with the calculated quantity of sulphuric acid. This pre- 
cipitates calcium sulphate and leaves ethyl sulphuric acid 
in the solution. It may now be isolated by evaporation 
of the solvent at moderate temperature. The product is a 
syrupy liquid soluble in water. Esters of this type, such as 
methyl sulphuric acid, break up on heating into sulphuric 
acid and the neutral ester. 

2 x S0 2 =H 2 S0 4 + ^SO a . 

HO/ CH 3 -0/ a 

Neutral methyl sulphate can be prepared in this way. It 
is employed as a reagent for introducing the methyl group. 
For this purpose it is almost as useful as methyl iodide and 
has the practical advantage of being much cheaper. 

Among other esters of the inorganic acids which possess 
some practical importance may be mentioned ethyl nitrite 
and amyl nitrite, which both find some use in medicine. 
The former is commonly known as " sweet spirits of niter." 
The latter has a peculiar physiological action. Inhalation 
of its vapors produces sudden dilation of the blood vessels. 
It is also used to some extent as a reagent. 



ALCOHOLS AND THEIR DERIVATIVES 79 

ETHERS. 

If methyl iodide be treated with sodium methylate, a 
metathesis takes place in the sense of the equation: 

"CH 3 I + NaO-CH 3 = Nal + CH 3 -0-CH 3 , 
resulting in the formation of a gas of the formula: 

H H 

I I 

H-C-O-C-H. 

I I 

H H 

This substance is known as dimethyl ether. Its constitu- 
tion is sufficiently fixed by the method of preparation just 
given. It will be noticed that it is an isomer of ethyl 
alcohol, both substances having the empirical formula 
C 2 H 6 0. This substance, however, shows none of the char- 
acteristic reactions of the alcohols. It is the simplest rep- 
resentative of the class of substances called ethers. These 
may be looked upon as oxides of the alkyl radicles, of which 
the alcohols may be considered hydroxides; or they may be 
regarded as water in which both of the hydrogen atoms 
have been substituted by alkyls, just as an alcohol is water 
in which one of the hydrogens has been so replaced. 

Although acted upon by some reagents, it still holds as 
a general rule that the e thers are q uite indifferent _chem- 
icajly. This finds an adequate expression in the graphic 
formula, for the hydrogen atoms are all connected directly 
to carbon as is the case with the indifferent hydrocarbons, 
while the oxygen is between the carbon atoms and therefore 
is protected from disturbing influences. The ethers, then, 
are to be thought of as but slightly more reactive than the 
hydrocarbons, and therefore well adapted to serve as sol- 
vents in many chemical reactions. 

The most important member of the series, and the only 
one which can receive detailed consideration here, is the 



80 OUTLINES OF ORGANIC CHEMISTRY 

ordinary " ether " of commerce, or diethyl ether. This 
may be formed by the action of ethyl iodide upon sodium 
ethylate. It is, however, commercially prepared in a dif- 
ferent way. It has just been shown that when ethyl alcohol 
is treated with concentrated sulphuric acid, an acid ester 
called ethyl sulphuric acid is formed. When this ester is 
heated with an excess of alcohol, sulphuric acid is regen- 
erated and ether distills off: 

HO x C 2 H 5 -0 N 

(1) C 2 H 5 OH+ S0 2 = H 2 + S0 2 . 

HO / HO ' 

HO x C 2 H 5 N 

(2) C 2 H 5 OH+ S0 2 = H 2 S0 4 + O. 

C 2 H 5 -0/ C 2 H 5 / 

Advantage is taken of these two reactions in the com- 
mercial preparation of ether. To a mixture of sulphuric 
acid and alcohol kept at a constant temperature near 140°, 
alcohol is allowed to flow. As the ether formed in the 
second reaction distills off, the sulphuric acid, which is at 
the same time regenerated, reacts with more alcohol as 
indicated by equation (1). In theory, then, a given quantity 
of sulphuric acid should serve to change an unlimited quantity 
of alcohol into ether. Such an operation is called a " con- 
tinuous process " and those engaged in chemical manufac- 
ture find it economical to make as many as possible of the 
processes which they employ proceed in this way. In the 
case just cited, in practical work, some charring takes 
place, and the spent mixture occasionally has to be removed 
and the reaction again begun. Ether was prepared from 
alcohol by the action of sulphuric acid long before the 
theory of the process had been worked out, and hence the 
product received the name " sulphuric ether." This name 
is still in use commercially, and serves to remind us of the 
time when the substance was supposed to contain sulphur. 



ALCOHOLS AND THEIR DERIVATIVES 81 

Ether is a light volatile oil boiling at 34°. It is employed 
constantly as a solvent in chemical laboratories, and is 
useful as an anaesthetic in surgery, having been employed 
in this way for the first time in Boston in 1846. For pur- 
poses of this kind it is now generally preferred to chloro- 
form because it does not exert so depressing an effect upon 
the action of the heart. 

The other ethers need not be described here. It will be 
noticed that they are isomeric with those alcohols having 
the same number of carbon atoms. ~~ 

It should be added that it is possible to prepare " mixed " 
ethers, which contain different alkyl radicles attached to 
one atom of oxygen, thus if methyl iodide be treated with 
sodium ethylate, methyl ethyl ether is obtained. 
CHoI -I- Na-0-CH 2 -CH 3 = Nal + CH 3 -0-CH 2 -CH 3 . 



rfe 



CHAPTER IV. 

ACIDS AND THEIR DERIVATIVES. 

At the present time those substances are considered as 
acids which, in aqueous solution, undergo electrolytic dis- 
sociation yielding hydrogen ions. The latter are perhaps 
most easily recognized by their action upon indicators; thus 
a blue litmus solution is changed to red by their action. 
There are several classes of organic compounds which possess 
acidic properties to a greater or less degree. By far the 
most important of these comprises those substances whose 
formulae contain a carboxyl group. It is of these com- 
pounds that one_us ually thinks w hen the—term ..." organic 
acid " is employed, and it is to these alone that attention 
will be called in the pages immediately following. 

The student is already sufficiently familiar with some of 
the methods of preparing the acids to permit a discussion 
of their constitution at this point. This discussion practi- 
cally limits itself to the proof of the presence of a carboxyl 
group. For the acid of the lowest molecular weight, formic 
acid, this is very simple, since no formula is possible for a 
monobasic acid of the composition CH 2 2 except 

H 

I 
C=0. 

\ 

OH 

In the case of the higher members of the series, this particu- 
lar form of reasoning cannot be used, though the fact that 
these show similarity to formic acid in their behavior might 

82 



ACIDS AND THEIR DERIVATIVES 83 

well be considered as an argument for analogous constitu- 
tion. Beyond this, however, it is fortunately possible to 
furnish direct proof in these cases also. Acetic acid may 
be taken as an example. Attention is first called to the two 
following equations : 

(1) CH 3 I + KCN = KI + CH 3 -CN. 

(2) CH 3 -CN + 2H 2 = NH 3 + CH3-COOH. 

In the first place, methyl iodide can have no other formula 
than that here assigned to it. It follows that both methyl 
cyanide and acetic acid contain a methyl group. On page 75 
equation (2) has already been used to prove that methyl 
cyanide has its two carbons directly connected. Putting 
these together the following skeleton formula is obtained: 

H x / 

H-C-C-. 

H 7 x 

From this the further conclusion may be drawn that both 
of the oxygens in acetic acid are connected to one carbon 
atom. Now it has already been stated that the acids have 
one hydrogen which may be replaced by a metal, and it is 
also true that under the influence of phosphorus chloride 
an oxygen and a hydrogen may be substituted by a single 
chlorine atom. When studying the alcohols (page 57), 
it was shown that these reactions are characteristic of the 
hydroxyl group. Adding this to the part of the formula 
already established, the result is 

H-C-Cf • 

hx x oh 

This leaves two bonds as yet unaccounted for, and this is 
just sufficient to unite with the two bonds of the remaining 



84 OUTLINES OF ORGANIC CHEMISTRY 

oxygen. It follows that the constitution of acetic acid is 
appropriately represented by the symbol, 

H^C-Cf . 
H/ x OH 

This is commonly abbreviated to the form, CH 3 — COOH. 
Similar reasoning, the details of which need not be repeated 
here, serves to establish the formula? of the higher members 
of the series. Before leaving the subject of the constitution 
of the acids, a word should be said concerning the specific 
influence of that oxygen atom which is united to carbon by 
two bonds. The presence of this carbonyl^roup^ consti- 
tutes the difference between an acid "antT^n alcohol, and 
this consists chiefly in a greater reactivity of the hydroxyl 
group and in particular of its hydrogen. This is rather 
more easily replaced than in the alcohols, and it is ionized 
in aqueous solution, which, as has already been pointed out, 
is not the case with the alcohols. This effect of the car- 
bonyl group is frequently spoken of as making the substance 
in which it occurs more " negative," a term which is not 
exactly easy to define. The words positive and negative 
are, however, frequently employed in Organic Chemistry to 
express a very useful but somewhat intangible idea of this 
sort. 

The principal general methods for the preparation of the 
acids have been already touched upon. They may be pre- 
pared by the hydrolysis of the corresponding nitriles and 
by various oxidation processes. The fact that they are 
formed by the oxidation of aldehydes having the same 
number of carbon atoms, and also from ketones having a 
larger number, has already been mentioned- Other methods 
involving oxidation will be met with later. 

Among the chemical reactions which are common to the 
acids, probably the most important and characteristic is their 



ACIDS AND THEIR DERIVATIVES 85 

action upon metals and bases which results in the formation 
of salts : 

//° 

CH3 — C V 

//° ° 

(1) 2CH 3 -Cf +Zn = H 2 -f ^Zn. 



CH 3 -C 



^O 



(2) CH 3 -Cf 4- KOH = H 2 0+CH 3 -Cf • 

x OH x OK 

It has been shown that they react with alcohols to form 
esters. This is facilitated by the addition of condensing 
agents which remove the water formed in the reaction: 

(3) CH 3 -C^ +HOC 2 H 5 = H 2 0+CH 3 -C^ 

x OH v OC 2 H ; . 

Reference has also already been made to the fact that, 
like that of the alcohols, the hydroxyl group of the acids 
may be substituted by halogens on treatment with the 
halides of phosphorus, for example: 

(4) CH 3 -Cf +PC1 5 = HC1 + P0C1 3 +CH 3 -C^ - 
x OH X C1 

The product of this reaction is called an acid chloride. 
The properties and behavior of such compounds will be 
dealt with later, along with those of the other acid deriva- 
tives. 

Another familiar reaction is that which was applied in 
the preparation of methane (page 37). The salts of the 
acids when distilled with the alkalies or with lime yield 
hydrocarbons containing one less atom of carbon than the 
original acid. "*\ 

(5) CH 3 - CH a - COONa + NaOH = Na 3 C0 8 + CH 8 - CH t . 



86 OUTLINES OF ORGANIC CHEMISTRY 

Formic Acid. (Latin, formica, an ant.) This acid, as 
its name implies, occurs in the bodies of ants, and it was 
obtained by early chemists from that source. The general 
methods of preparation already cited are applicable to the 
formation of this acid; thus it is produced by the oxidation 
of formaldehyde, and by the hydrolysis of hydrocyanic acid, 
which may be regarded as its nitrile. Neither of these 
methods, however, is of practical importance. The most 
common laboratory method for its preparation consists in 
heating oxalic acid with glycerin. Under these circum- 
stances the former substance breaks up into carbon dioxide 
and formic acid : 

C 2 H 2 4 = C0 2 + HCOOH. 
According to its formula CO, carbon monoxide might be 
regarded as the anhydride of formic acid. Now though 
the gas does not unite with water like other acid anhydrides 
to form the acid, yet when it is passed through a solution 
of sodium hydroxide under pressure, and at a temperature 
just below 220°, sodium formate is produced. This process 
is now in use technically for manufacturing the acid. The 
product yielded by any of these methods contains water, 
from which it cannot be separated by distillation, since the 
two liquids form a mixture which distills at constant tem- 
perature. One of the methods of obtaining the anhydrous 
acid is to prepare the lead salt by the action of lead oxide 
upon the aqueous acid. This is soluble with difficulty and 
beautifully crystalline. At 100°, it may be decomposed 
by dry hydrogen sulphide, forming lead sulphide and anhy- 
drous formic acid. 



H-<° 





) Pb + H 2 S = PbS + 2 HCOOH. 
O 



H-C' 
^0 



ACIDS AND THEIR DERIVATIVES 87 

Another method of dehydration is to mix the strong aqueous 
acid with its sodium salt, and then add dry concentrated 
sulphuric acid and distill. Pure formic acid is a colorless 
liquid of sharp irritating odor. Its specific gravity is 1.2187 
at 20°. It boils at 101°, and freezes at 8°. It is miscible in 
all proportions with water. The anhydrous acid produces 
extremely disagreeable effects upon animal tissue, a drop 
falling upon the skin often causing a painful wound. 

Formic acid finds some technical use as a substitute for 
acetic acid, which in the past few years has been increasing 
in price. It is also used for some operations in dyeing and 
tanning, where a combination of acid and reducing proper- 
ties is required. 

Although a weak acid when compared with the mineral 
acids like hydrochloric, formic acid is by far the strong- 
est member of its series. Thus its dissociation constant is 
0.0214 at 25°. That is to say, it is about twelve times as 
strong as acetic acid, for which the dissociation constant 
is 0.0018. The other acids of this series have constants 
which do not differ much from the latter value. This 
sudden falling off in the strength of the acids after the first 
member has been passed, is an illustration of one of the pecu- 
liarities often noticed in homologous series. It is frequently 
the case that the first member of such a series, especially 
when it contains but one atom of carbon, shows less resem- 
blance to the next member than this exhibits to those that 
follow. This is not surprising when it is considered that 
such substances as formic acid, methyl alcohol, and the 
like contain no alkyl radicle, whereas all their homologues do. 
This peculiarity of the lowest members of homologous series 
has an interesting analogy in Inorganic Chemistry. The 
student will already be familiar with the fact that something 
similar holds true of the elements with lowest atomic weight 
in each group of the Periodic System. Fluorine, for example, 



88 OUTLINES OF ORGANIC CHEMISTRY 

is much less similar to chlorine than this is to bromine and 
iodine; while beryllium differs as widely from barium, 
strontium, and calcium. 

Acetic Acid. The constitution and the laboratory 
methods of preparation for this acid have been already 
considered (page 83). It may be formed by the oxidation 
of the aldehyde or by the saponification of the nitrile, — 
methyl cyanide. 

Two technical methods of preparation have to be added. 
One of these is suitable for the production of a concentrated, 
the other of a dilute acid. 

When hard woods like birch or beech are distilled, tar is 
obtained, and also an aqueous distillate commonly known 
as " pyroligneous acid." This last contains, besides water 
and numerous impurities, three important organic compounds 
of which it furnishes the chief technical source. These are 
methyl alcohol, acetic acid, and acetone. In the process 
of distillation the hot vapors are usually allowed to strike 
through lime, and this takes up the acetic acid, forming 
calcium acetate. By distillation with sulphuric acid, the 
latter yields crude acetic acid. The pure acid can be obtained 
from this product by fractional distillation. This sub- 
stance has a sour taste and characteristic sharp odor. It 
has the specific gravity 1.0502, melts at 16° and boils at 
118°. Since its melting point is so high, the pure jtcjuiis- a 
crystalline solid on cool days, and this has given it the name 
" glacial acetic acid." It finds employment in the labora- 
tory both as a solvent and as a reagent, as well as to some 
extent technically; the dilute solution is particularly useful 
where a weak acid is required. The sodium and lead salts 
are familiar reagents, while the salts of iron, aluminium, 
and chromium find extensive use as mordants in dyeing. 
The theoretical considerations underlying this process will be 
taken up in connection with a study of the dyes themselves. 



ACIDS AND THEIR DERIVATIVES 89 

A dilute solution of acetic acid is the principal constituent 
of vinegar (Latin, acetum). This was originally prepared 
by the " souring" of wine or cider under the influence of 
certain micro-organisms, collectively known as "mother of 
vinegar.'' Vinegar is now largely manufactured by what 
is known as the "rapid vinegar process." This is carried 
out as follows. Casks supplied with holes for the admission 
of air are loosely rilled with beech shavings. Over these 
is first poured old vinegar in order to distribute upon the 
surface of the shavings sufficient micro-organisms to start the 
fermentation. A dilute solution containing about 10 % of 
alcohol is allowed to trickle over these. Fermentation sets 
in, the temperature rises, and a 4 % to 6 % solution of acetic 
acid runs off. The original product thus formed is color- 
less, but coloring and flavoring materials are usually added 
before it is brought upon the market. 

Propionic Acid. (Greek, 7rpa>Tos, first and tuW, fat.) This 
acid derives its name from the fact that it was formerly 
regarded as the first of the fatty acids. This original 
significance has, however, been practically lost since the 
term "fatty acids" has come to include the whole series 
from formic acid up. The substance is a colorless liquid 
of a sharp, somewhat rancid odor. It is soluble in water, 
but may be separated from such solutions by the addition 
of calcium chloride. It is of little practical importance. 

Butyric Acids. Two acids are theoretically possible 
having the formula C 4 H 8 2 , and both are known, 

CH 3 . 
CH 3 - CH 3 - CH 3 - COOH and ; CH - COOH. 

ch/ 

The normal acid occurs as a glycerin ester in butter, and 
from this source it has received its name. The free acid 
occurs also in the fseces and in perspiration, so that its odor 
has come to have many disagreeable associations. Butyric 



90 OUTLINES OF ORGANIC CHEMISTRY 

acid is most conveniently prepared from sugar by a fer- 
mentation process, under the influence of certain micro- 
organisms found in decaying cheese. Lactic acid is then 
formed as an intermediate product. The isomeric acid, 
commonly known as isobutyric acid, is also formed in certain 
fermentation processes and occurs to a limited extent in 
nature. It much resembles the normal acid in physical and 
chemical properties, and has little specific importance. In 
this respect these acids may serve as types of most of the 
members of the series containing from four to ten atoms of 
carbon. It is unfortunate that these acids do not, like the 
alcohols and alkyl radicles, possess names based upon the 
Greek numerals. Instead, they all have trivial names. 
Few of those higher than butyric acid, however, have so 
much importance that the student need burden his memory 
with their names or properties. Attention should be called 
to the interesting fact that, among the higher members of 
the series it is almost exclusively the normal members, con- 
taining an even number of carbon atoms, which are found in 
nature. Those with an odd number are either not met with 
or are extremely rare. 

The acids of this series which contain twelve or more atoms 
of carbon are solids which no longer possess the disagreeable 
odor of butyric acid and its neighboring homologues. On the 
contrary, they resemble the fats, in which they largely occur 
as esters of glycerin. By far the most important are palmitic 
and stearic acids which as glycerin esters make up iTTaTge 
proportion of the natural fats. These acids are the normal 
compounds containing sixteen and eighteen carbon atoms 
respectively. Their alkali salts along with those of oleic 
acid, a member of another series, form the soaps. All these 
matters will again be taken up in connection with the 
technology of the fats. 



ACIDS AND THEIR DERIVATIVES 91 

THE ACID DERIVATIVES. 

Under this head belong certain substances which are 
closely associated with the acids. There are several classes. 
Those which will be considered here are the acid chlorides, 
anhydrides, esters, and amides. 

Acid Chlo rides. It is characteristic of the hydroxyl 
group that when substances which contain it are treated 
with the halogen compounds of phosphorus, the hydroxyl 
group is replaced by halogen; thus, as has already been 
shown, acetic acid reacts as follows: 

CH 3 . CO . OH + PC1 5 = HC1 + POCI3 + CH 3 - CO . CI, 

forming hydrochloric acid, phosphorus oxychloride, and acetyl 
chloride. The last is a colorless liquid boiling at 51°, and 
having the specific gravity 1.05 at 20°. It possesses a sharp, 
intolerable odor, and its vapors violently attack the mucous 
membrane of the eyes and nasal passages. It fumes in the 
air on account of the vigorous reaction into which it enters 
with water. The two substances unite with almost explosive 
violence. The products formed are acetic acid and hydro- 
chloric acid: 

CH 3 -C( +HOH=CH 3 -C; +HC1. 
3 X C1 3 x OH 

Another very important reaction of this substance is that 
with the alcohols. Here hydrochloric acid is produced and 
an acetate of the alcohol: 

CH 3 - C ( + HOC 2 H 5 = HC1 +CH 3 - C ' 

X C1 5 3 x OC 2 H 5 

This reaction, it will be noticed, is analogous to the pre- 
ceding, and justifies the conception of the alcohols as water 
in which hydrogen has been replaced by an alkyl. 

This is one of the reactions which make acetyl chloride so 
valuable as a reagent, for, by its aid, it is possible to deter- 



92 OUTLINES OF ORGANIC CHEMISTRY 

mine how many of the oxygens in an unfamiliar compound 
are of alcoholic character. It is generally true that when 
acetyl chloride reacts with substances containing several 
hydroxyl groups, each of these is substituted by the acetic 
acid radicle. 

Acetyl chloride shows many other important reactions 
which it would be impracticable to enumerate at this time. 
Suffice it to say that the carbonyl group, by its negative 
character, makes the halogen atom to which it is directly 
attached more reactive even than that in the alkyl halides 
themselves. This halogen takes part in the most diverse 
metathetical reactions. Some of these will be considered 
later when the products formed come up for discussion. 

The higher homologues of acetyl chloride resemble it closely 
in physical and chemical properties. They show only such 
variations as are familiar to the student from the study of 
other homologous series. Most of the individual compounds 
of this series are, however, rarely met with in practice, and 
will receive no further consideration here. 

No chloride of formic acid is known. Reactions which 
might be expected to form this compound yield instead a 
mixture of carbon monoxide and hydrochloric acid. It is 
an interesting fact that under certain conditions a mixture 
of these gases reacts as if a chloride of formic acid were 
present. 

The nomenclature of the series of acid chlorides is impor- 
tant because it introduces another series of radicles whose 
names will be frequently met with. The name " acetyl 
chloride" implies that the substance is a binary compound 
of chlorine with the monovalent radicle, acetyl, which has 
the formula, 

CH 3 
I 

c = o. 

1 



ACIDS AND THEIR DERIVATIVES 93 

For every acid there must exist a similar radicle, the formula 
of which may be obtained by taking the hydroxyl group 
away from the formula of the acid. Thus from acetic acid, 
CH 3 — COOH, may be derived acetyl, CH 3 — CO; from 
propionic acid, CH 3 — CH 2 — COOH, propionyl, CH 3 — 
CH 2 - CO; from butyric acid, CH 3 - CH 2 - CH 2 - COOH, 
butyryl, CH 3 - CH 2 - CH 2 - CO; and so forth. Collec- 
tively these are known as the acyl radicles, and the 
manner of naming the individual members is sufficiently 
obvious from the examples just given. The essential thing 
to be remembered about the acid chlorides is that they are 
chlorides of the acyl radicles, and their chemical signifi- 
cance lies chiefly in the fact that they serve to introduce the 
acyl group into other organic compounds. 

The 4cjd Anhydrides. When acetyl chloride is heated 
with sodium acetate, sodium chloride is formed and acetic 
anhydride: ^ Q ^ 

CHo — C v + "va /C — CHo = 
X C1 NaO 7 

//00, x 
NaCl + CH 3 - C . / C- CH 3 . 

^O^ 
The latter may be distilled off. It is a colorless liquid of a 
sharp odor somewhat resembling that of the free acid, but 
more penetrating. It boils at 136°, and has the specific 
gravity 1.078 at 21°. This substance is a type of the large 
class of compounds known as acid a nhydrides . 

As indicated by their formulae, these substances may be 
regarded as the product formed by removing one molecule 
of water from two molecules of a fatty acid: 

CHo — C v /,0 

x OH CH 3 -cf 

+ = E 2 + ,0 



OH CHo-C' 



CH, -cC ~^0 



O 



94 OUTLINES OF ORGANIC CHEMISTRY 

Some of the acid anhydrides may, as a matter of fact, be 
prepared by treating the acids with dehydrating agents as 
the above equation suggests. There is considerable variety 
in the behavior of the acids in this respect. Some require 
the use of the most vigorous dehydrating agents in order to 
remove the water, while others lose water when distilled. 
Some of the anhydrides of the higher acids may even be 
heated with water for some time without noticeable regen- 
eration of the acid. Acetic anhydride, however, and its 
neighboring homologues, while they do not react quite as 
vigorously with water as do the acid chlorides, yet are rapidly 
decomposed by it in the manner indicated by the following 
equation : 



CEL -C 



// 



3 x + H 2 = 2CH 3 - COOH . 
CH 3 - C ( 

With alcohols and many other substances, the anhydrides 
behave quite similarly to the chlorides. Thus with the 
alcohols they substitute the hydrogen of the hydroxyl group 
by an acyl radicle forming esters. In this way acetic anhy- 
dride reacts with ethyl alcohol forming ethyl acetate: 



// 



O 



CH.-C* o 

) O + HOC 2 H 5 = CH 3 - COOH + CH 3 - C f 
CH 3 -C( o x OC 2 H 5 

The acid anhydrides boil higher than the corresponding 
acids, while the chlorides boil materially lower. It follows 
that when a high temperature is required, the anhydrides 
are preferred to the chlorides as acylating agents. 

Esters. Esters may be denned as acids in which the 
hydrogen of the carboxyl group has been replaced by an 
alkyl radicle. A good deal has already been said concerning 



ACIDS AND THEIR DERIVATIVES 95 

this important class of substances, and the esters of the 
inorganic acids have been dealt with in some detail. Three 
general methods of preparation have been mentioned: — 
the action of an acid directly upon an alcohol: 

CH 3 -Cf + HOC 2 H 5 = CH 3 -Cf +H 2 0; 

\OH x OC 2 H 5 

the action of an acid chloride upon an alcohol : 

CH 3 -CH a -Cr + HOC 2 H 5 = CH 3 -CH,-Cf +HC1; 

^Cl ; 5 3 . N OC 2 H 5 

and the action of the anhydride of the acid upon the alcohol: 

CH 3 -C^ O 

^0+HOC 3 H 7 = CH 3 -Cf +CH 3 -COOH. 

CH 3 -C( x OC 3 H 7 

3 %o 

A fourth method consists in treating the salt of an acid with 
an alkyl halide; thus methyl acetate may be prepared by 
treating silver acetate with methyl iodide: 

CH 3 -CT + I-CH 3 = AgI-fCH 3 -Cf 

x OAg x OCH 3 

Of these methods, by far the most important is the first 
mentioned, which consists in the action of the acid upon the 
alcohol. This reaction is a reversible one, that is, by the 
action of water the ester is again decomposed into alcohol 
and acid. 

It will be profitable to study the relations which obtain 
here with a good deal of care, because the process of ester- 
formation was, historically, one of the earlier reactions 
studied in the establishment of the mass action law, and it 
still serves as an especially good illustration of that important 
generalization. 



96 OUTLINES OF ORGANIC CHEMISTRY 

If an acid is mixed with an alcohol the reaction typified 
by the following equation, 

CH 3 - C ( oh + HOC 2 H 5 *± H 2 + CH 3 COOC 2 H 5 , 

will begin to proceed from left to right at a certain velocity. 
As soon as any ester and water have been formed, however, 
they will begin to react in the sense of the same equation 
when read from right to left.. The net result of this will 
be to cut down the quantities of ester and water formed in a 
given time. As more ester and water are formed, the second 
reaction increases in velocity while the first diminishes,. A 
p oint is finally reached where the velocity of saponification i s 
e qual to that of est erification. This is a chemical equilibrium; 
that is, beyond this point analysis will show no further change 
in the proportions of alcohol, acid, ester, and water present 
in the reacting mixture. 

If instead of a mixture of acid and alcohol, a similar 
mixture of the ester and water had been taken, something 
entirely analogous would have occurred. In this case saponi- 
fication would have proceeded with constantly diminishing 
velocity until equilibrium was reached, and at this point the 
relative concentrations of the four reacting components 
would be exactly the same as it was in the first case. That 
is to say, in any reversible reaction, the same equilibrium 
is reached from whichever direction it is approached. 

The fundamental relationship expressed by themass action 
law is the fact that the velocity with which a reaction takes 
place is directly proportional to the products of the molecular 
concentrations of the reacting components. Translated into 
the terms of the present case, this means that the velocity 
of esterification, for example, is proportional to the number 
of molecules of acid present in unit volume multiplied 
by the number of molecules of alcohol. A perfectly similar 



ACIDS AND THEIR DERIVATIVES 97 

statement can be made concerning the velocity of saponi- 
fication. This is proportional to the product of the molec- 
ular concentrations of ester and water. 

Now when equilibrium has been reached, the velocities of 
esterification and saponification are equal. Hence, at this 
point, the product of the concentrations of acid and alcohol 
must stand in a fixed relation to the product of the con- 
centrations of ester and water. This relation may be con- 
veniently expressed mathematically as follows : — 
mol. cone, of acid X mol. cone, of alcohol _ 
mol. cone, of ester X mol. cone, of water 

For a given reaction it is not difficult to determine the 
numerical value of this constant. Experiment has shown 
that when acetic acid and ethyl alcohol are mixed in equi- 
molecular quantities, that is, in the proportion of 46 grams 
alcohol to 60 grams acetic acid, equilibrium is established 
when two-thirds of a mol of both ester and water have been 
formed. The condition in the reacting mixture at this point 
finds expression in the following equation: 

or J is the constant of this particular reaction. 

Verification of the law is found in the fact that when the 
proportions of acid and alcohol originally taken are varied 
most widely, the reaction always proceeds in such a way 
that when equilibrium has been reached, and the molecular 
concentrations found present in the reacting mixture are 
substituted in the above equation, the same constant, \, 
is always obtained. 

The applications of the mass action law are extremely 
important and far-reaching. Only one will be considered 
at this point. In chemical work, questions like the follow- 
ing are of frequent occurrence: — From a given amount of 
acid (or alcohol) how may the maximum quantity of ester 



98 OUTLINES OF ORGANIC CHEMISTRY 

be obtained? The mass action law suggests two ways by 
which the yield of ester may be improved. One is the 
elimination of water from the reaction. Since at equilibrium 
the products of the concentrations of ester and water must 
have a certain value, decrease in the quantity of water must 
increase the amount of ester formed. It is, of course, 
impossible to remove all the water from the reacting mixture, 
but the addition of dehydrating agents is a general practice 
in carrying out esterincation processes. 

The yield may be further influenced in another way. 
It follows from the law that the product of the concentra- 
tions of ester and water at equilibrium will be increased 
if the product of the concentrations of alcohol and acid are 
also increased, and since, by the terms of the problem, one 
of these quantities — the acid for example — is limited, the 
end can be attained by increasing the quantity of the other 
constituent, — in this case the alcohol. What can be accom- 
plished in this way is best indicated by calculating the yield 
in a specific case. 

Let it be supposed that one mol of acetic acid has been 
treated with four mols of ethyl alcohol, and that, at equilib- 
rium, x mols of ethyl acetate have been formed. Then it is 
evident from the equation, 

CH 3 - COOH + HOC 2 H 5 <r±H 2 + CH 3 - COOC 2 H 5 , 
that for every mol of ester, one mol of water is also formed, 
consequently the water present may also be represented 
by x. Similarly, for each mol of ester formed, one mol of 
acid and one of alcohol are used up, hence the quantities of 
these substances present in the reacting mixture at equilibrium 
may be represented by 1— x and 4 — x respectively. Mak- 
ing these substitutions in our fundamental equation (page 97) 
we obtain the following: 

(1-30(4-3?) 1 

x 2 ~4' 



ACIDS AND THEIR DERIVATIVES 99 

The solution of this equation yields the result, x = 0.93. 
This means that when one mol of acetic acid is treated with 
four mols of ethyl alcohol, 0.93 mol of ester is formed, 
whereas it has already been shown on page 97 that when 
the acid and alcohol are employed in equimolar quantities, 
but 0.66 mol of ester is produced. 

The relation of the mass action law to esterification proc- 
esses has been considered here in so much detail because 
it is applicable to all reversible reactions, and recent investi- 
gations have shown that many reactions which had formerly 
not been considered reversible in reality are so. Indeed 
many assert that all chemical reactions are reversible, but 
that, in certain cases, at equilibrium, the concentration of 
one or more components is so small as to escape observa- 
tion with any means at our command. Without going so 
far as this somewhat dogmatic statement might imply, it 
is certainly true that many of the most important chemical 
reactions are reversible, that reversible reactions predomi- 
nate in the organic field, and, consequently, that the re- 
actions of organic compounds are best understood when 
they are looked upon as steps leading to a chemical equi- 
librium. 

Turning back to the chemistry of the esters themselves, 
it is obvious that since any alcohol may unite with any acid 
to form an ester, the number of these compounds theoret- 
ically possible defies computation. Esters are usually pre- 
pared in the laboratory by heating together the alcohol and 
acid in the presence of some condensing agent, usually 
either concentrated sulphuric or gaseous hydrochloric acid. 

Ethyl acetate may serve as a type of the esters formed by 
the action of the lower fatty acids upon the lower alcohols. 
It is a colorless liquid boiling at 77°, and it has the specific 
gravity 0.924 at 0°. It has an agreeable, sweetish odor, 
usually described as " fruity." An odor of similar character 



100 OUTLINES OF ORGANIC CHEMISTRY 

is possessed by most compounds of this type. They are 
used somewhat as perfumes and in producing the " bouquet " 
of artificial wines. Ethyl acetate itself is manufactured 
in considerable quantity as an intermediate product in the 
preparation of " antipyrine," a popular fever remedy. 

The esters of the higher fatty acids with the higher alco- 
hols constitute the chief ingredients of the natural waxes, 
of which beeswax is a familiar example. Spermaceti, a wax 
occurring in the head of the sperm whale and used to a cer- 
tain extent for making candles, contains, as principal ingre- 
dient, cetyl palmate, having the formula, C 15 H 31 «COOC 16 H 3 3. 

The esters which occur most widely in nature, as well as 
those of the highest technical utility, include compounds of 
alcohols and acids belonging to other series. The student 
will therefore not be in a position to realize the full impor- 
tance of this class of substances until somewhat later. 

The most important and characteristic reaction of the 
esters has been already noted. It is the s£Htting_actipn 
which hydrolytic agents have upon them, producing alcohol 
and acid. In laboratory practice, this is carried out by 
boiling the ester with alkalies or dilute acids. The action 
of alkalies is easily understood. They unite with the acid 
as rapidly as it is formed, and so eliminate it as a factor 
in the reversible reaction which we have just studied. When 
saponification is effected by acids, the action of the latter is 
catalytic, that is to say, they promote saponification with- 
out being themselves used up by the reaction. 

This catalytic action of the acids has proved an important 
support of the theory of electrolytic dissociation, for the 
hydrolyzing action of the acid has been shown to belong to 
the hydrogen ion. All acids show the property in some 
degree, and the velocity of saponification caused by different 
acids is proportional to their respective degrees of dissocia- 
tion as determined by measurements of electric conductivity. 



ACIDS AND THEIR DERIVATIVES 101 

The Amides. These compounds are closely associated 
with the acids, and furnish a convenient means of identifying 
the latter, since they are, for the most part, crystalline solids 
of sharp and characteristic melting point. They also appear 
as intermediate products in important reactions. The acid 
amides may be prepared by the action of ammonia upon the 
acid chlorides, the anhydrides, and the esters, in accordance 
with the following equations : 

(1) CH 3 -C( ci + 2NH 3 = CH,-(\ nh +NH,C1, 

(2) )0 + 2NH 3 = CH 3 -C( +CH 3 -Cf 
CH 3 -CT X NH, v ONH 4 

(3) CH 3- C \ 0CH + NH s = CH 3 -C Xnh +C 2 H 6 OH. 

When the ammonium salts of the acids are heated, they read- 
ily lose water and go over to amides: 

(4) CH 3 - C ( = H 2 + CH 3 - C ( 

x ONH 4 2 X NH 2 

The amides themselves, on treatment with dehydrating 
agents such as phosphorus pentoxide, yield the nitriles of 
the acids : O 

CH,-c' = ILO + CH,-CN. 



\ 



NH 2 



These reactions place the amides as intermediate products 

between the nitriles and the acids in the saponification of the 

latter: q 

CH 3 - CN + H 2 = CH 3 - c( 

3 X NH 2 ' 

CH 3 -C. ttt + H 2 - CH 3 - COONH 4; 

rsH 2 



102 OUTLINES OF ORGANIC CHEMISTRY 

(see page 75) and they can sometimes be thus obtained by 
careful regulation of the experimental conditions. 

The methods of preparation furnish the experimental 
evidence for the formula given. This represents the amides 
as acids in which hydroxyl has been substituted by NH 2 , 
the amino-group. It is also possible to regard these sub- 
stances as ammonia in which one hydrogen has been sub- 
stituted by an acyl radicle. 

So far as chemical behavior is concerned, one of their 
most important reactions has been already mentioned. This 
is the fact that they may be hydrolyzed to form acids. In 
practice this is usually accomplished by boiling with alkalies, 
when the alkali salt of the acid is formed, and ammonia is 
evolved: 

CH 3 -C( +KOH = CH 3 -C( + NH 3 . 
X NH 2 x OK 

The amides show certain other important reactions; con- 
sideration of which must be postponed until the study of 
some of the other classes of nitrogen compounds has been 
taken up. 

Acetamide is a hygroscopic, crystalline solid. As usually 
prepared, it contains some impurity, having an odor sug- 
gestive of mice. The pure amide is, however, odorless. It 
melts at 82°. The other acid amides of this series do not 
have sufficient individual importance to make it worth 
while to enumerate their physical properties. 



CHAPTER V. 

ALDEHYDES, KETONES, AND AMINES. 

It has already been shown (page 65) that when the 
primary alcohols are oxidized to acids, the aldehydes appear 
as intermediate products. This relationship may be indi- 
cated by the following scheme in which R represents any 
alkyl radicle: 

^H 2 /H /y O 

R — C v > R — C ,x > R — C v 

x OH ^O x OH 

The formula? for acids and the alcohols having been already 
established, that of the aldehydes can scarcely be in doubt. 
The formula of an aldehyde, then, is characterized by the 

I 
possession of the carbonyl group CO, united on one side to 

I 
an alkyl radicle and on the other to hydrogen. 

Though the aldehydes can be obtained by the oxidation 
of the alcohols, they cannot be conveniently prepared by 
the direct reduction of the corresponding acids. The most 
common way of passing from an acid to the corresponding 
aldehyde is to distill the calcium salt of the acid with calcium 
formate : 

^O O^ 

R-cf ;c-h 

o 

)Ca+Ca( =2CaC0 3 +2R-cf' ' 

O V H 

R — C,v z.C — H 

^0 - O y 

103 



104 OUTLINES OF ORGANIC CHEMISTRY 

This is an extremely important and general reaction for the 
preparation of compounds containing the carbonyl group. 
The names of the aldehydes (except in those cases where 
trivial names are employed) are derived from those of the 
corresponding acids; thus we have the names formaldehyde, 
acetaldehyde, and the like. 

As a rule, the aldehydes boil lower than either the acids 
or alcohols having the same number of carbon atoms. 
The lower members of the series have a peculiar penetrating 
odor. In general it may be said that the odors of the alde- 
hydes are strongly marked, and in the majority of cases 
agreeable. 

Chemically the aldehydes are extremely reactive. One of 
the most characteristic items in their behavior is the ease 
with which they are oxidized to form the acids having the 
same number of carbon atoms. On account of this peculiar- 
ity they serve as reducing agents. They reduce, for exam- 
ple, metallic silver from ammoniacal solutions of its salts: 
2 AgN0 3 + CH3CHO + 3 NH 4 OH = 

CH 3 COONH 4 + 2 NH 4 N0 3 + 2 H 2 + Ag 2 , 
and they reduce alkaline solutions of cupric salts with the 
formation of cuprous oxide. A typical solution of this kind 
is that commonly known as "Fehling's solution." It is 
prepared by mixing solutions of copper sulphate, potassium 
hydroxide, and sodium potassium tartrate in such propor- 
tions that cupric hydroxide shall not be precipitated by the 
alkali. 

Aldehydes show numerous and important addition reac- 
tions, thus ammonia is added in accordance with the equa- 
tion, 



CH 3 


CH 3 


1 

C = 0+ NH 3 

1 

H 


1 /OH 

1 X NH 3 
H 



ALDEHYDES, KETONES, AND AMINES 105 

With sodium bisulphite^also, addition products are formed: 

CH 3 CH 3 

I I /OH 

C = + HNaSO, = C v 

, , X S0 3 Na 

H H 

These compounds are crystalline and particularly useful for 
the separation and purification of the aldehydes, since they 
can easily be decomposed again by treatment with acids 
or alkaline carbonates, the aldehydes being regenerated. A 
reaction more important than either of the above is that 
which takes place with hydrocyanic acid: 

CH 3 CH 3 

I I .OH 

C = O + HCN = C v 

H H 

The resulting product is the nitrile of a hydroxy-acid : 

CH 3 

I /OH 
C 

I x COOH 

H 

This illustrates a general method for the preparation of those 
acids which have a hydroxyl group attached to that carbon 
atom which is next to the carboxyl. This is termed the 
alpha carbon atom. 

Another peculiarity of the aldehydes which may be men- 
tioned among the addition reactions is the tendency which 
they exhibit to polymerize; that is, several molecules of 
aldehyde combine to form a complex of the same percent- 
age composition as the original aldehyde but of higher 
molecular weight. Such polymerizations take place in sev- 
eral different ways, forming very diverse classes of products. 



106 OUTLINES OF ORGANIC CHEMISTRY 

Some of these will be described when the individual alde- 
hydes are studied. 

Still another class of reactions shown by aldehydes includes 
those involving condensation. This term is usually applied 
to those reactions where two compounds unite with elimi- 
nation of water or some other simple inorganic compound. 
When aldehydes take part in such reactions the oxygen of 
the carbonyl group usually unites with two hydrogen atoms 
of the other compound, and the remaining portions of the 
two compounds unite. Though aldehydes show many reac- 
tions of this type, but one will be mentioned here as an 
example. Hydroxylamine condenses with aldehydes in ac- 
cordance with the following equation: 



CH, CH 



C = O + H 2 N-OH = H 2 + C = NOH. 
I I 

H H 

The products are called oximes and they are characteristic 
derivatives of the aldehydes and ketones. 

One other reaction should be mentioned, since it serves 
to distinguish aldehydic from hydroxyl oxygen. It will be 
remembered that, upon the latter, phosphorus pentachloride 
reacts in such a way that the hydroxyl group is replaced by 
chlorine : 

C 2 H 5 OH + PC1 5 = HC1 + POCI3 + C 2 H 5 C1. 

With aldehydes, oxygen alone is replaced by two atoms of 

chlorine 7 " 

CH 3 CH 3 

I I /CI 

c = o + pci 5 = poci 3 + (\ • 

I I C1 

H H 



ALDEHYDES, KETONES, AND AMINES 107 

This reaction is of frequent application for the preparation 
of compounds having two halogen atoms attached to the 
same carbon atom. 

Formaldehyde. When the vapors of methyl alcohol 
mixed with air are passed over a warm metallic surface 
(platinum or copper may be employed), oxidation takes 
place upon the surface of the metal and formaldehyde is 
produced. The heat generated by the reaction is usually 
sufficient to keep the metal glowing. This method is car- 
ried out on a large scale for producing this substance for 
technical purposes. The quantities manufactured are very 
large, Germany alone producing annually about a half 
million kilograms. Formaldehyde is a gas of a peculiar 
sharp choking odor. It is quite soluble in water, and a 
40 % solution is brought upon the market under the name 
of " formalin." This is largely used as a preservative, for- 
maldehyde being an efficient germicide. The hardening 
action of this material upon substances of albuminous 
character makes it useful in many branches of industry. 
The gas itself is used for disinfecting purposes, advantage 
being frequently taken of the method of preparation out- 
lined above. Methyl alcohol is burned in a specially con- 
structed lamp which permits only incomplete combustion, 
with consequent formation of the aldehyde. The gas may 
be condensed to a liquid by low temperatures. This liquid 
boils at —21°. The polymerization of formaldehyde yields 
several products whose molecular weight is uncertain. 
When a solution of formalin is evaporated, an amorphous, 
white solid is precipitated known as paraformaldehyde. 
This substance has the odor of the gas, and is soluble in 
water, such solutions differing in no respect from those 
formed when formaldehyde itself is dissolved in water. If 
formalin solution be treated with small amounts of con- 
centrated sulphuric acid, a mixture of products is obtained, 



108 OUTLINES OF ORGANIC CHEMISTRY 

all of which are solid. These are known as polyoxy methylenes 
and are not well characterized. The aqueous solution of 
formaldehyde doubtless represents an equilibrium between 
the monomolecular compound and several of the polymers. 
From formaldehyde vapor, under certain conditions, may 
be formed still another substance, — a-oxytrimethylene, — 
which, unlike those just mentioned, does not smell of formal- 
dehyde, and gives none of the aldehyde reactions. This 
substance has three times the molecular weight of the 
simple compound. 

Especial interest attaches to formaldehyde on account of a 
theory originally suggested by Baeyer to the effect that this 
substance is the first reduction product of carbon dioxide in 
the leaves of the green plant, and that the plant produces 
carbohydrates by the polymerization of formaldehyde. 
This theory, which has been under discussion for many years 
without having been found susceptible of definite proof, has 
much speculative interest. As will be seen when the study 
of the carbohydrates is taken up, it has been found possible 
to build up substances of this class from formaldehyde under 
certain conditions. On the other hand, only traces of form- 
aldehyde have ever been found in plants, and even at low 
concentrations it is an active poison for the plant cell. It 
is, however, a part of the theory that the formaldehyde is 
further polymerized as soon as it is formed. 

Acetaldehyde. This substance is usually prepared by 
the oxidation of ethyl alcohol by means of potassium bichro- 
mate and sulphuric acid: 

CH 3 
3 I + K 2 O 2 7 + 4H 2 S0 4 = 



CH 2 OH 



CH 3 
3 I + K 2 S0 4 + Cr 2 (S0 4 ) 3 + 7 H 3 . 
CHO 



ALDEHYDES, KETONES, AND AMINES 109 

It is an extremely volatile liquid boiling at 21°. It has a 
peculiar odor which, in strong dilution, is refreshing and 
agreeable. On the other hand, when the vapors are 
inhaled in concentrated form a peculiar cramp in the chest 
is produced, which temporarily takes away the power 
of breathing. Acetaldehyde shows all the typical alde- 
hyde reactions. It reduces ammoniacal silver nitrate solu- 
tion in the cold; when treated with ammonia gas in 
etheral solution a crystalline addition product called 
aldehy de-ammonia is precipitated; it adds sodium bisul- 
phite, etc. 

When acetaldehyde is treated with a very small quantity 
of concentrated sulphuric acid, polymerization takes place 
with almost explosive violence. The product is called 
paraldehyde. It is a liquid which boils at 124°, and 
shows none of the ordinary aldehyde reactions. Its vapor 
density indicates that three molecules of the original alde- 
hyde have united. When distilled with dilute sulphuric acid 
it is again depolymerized. If acetaldehyde be treated in 
the cold with hydrochloric, sulphuric, or sulphurous acid, 
there is formed in addition to paraldehyde a solid product 
called metaldehyde. This substance also has a molecular 
weight three times as great as the simple aldehyde. Its 
vapors dissociate again to the ordinary variety. Still another 
polymer is formed when aldehyde is boiled with alkalies. 
Tln^substance is a yellow gummy material known as aldehyde 
resin. It has an aromatic odor, and a study of its decom- 
position products goes to show that it is probably a deriva- 
tive of benzene. Acetaldehyde is almost always present in 
commercial alcohol, and betrays its presence by the yellow 
color which a solution of caustic soda or potash in such 
alcohol assumes. The color is due to the formation of a 
small quantity of aldehyde resin. 

The higher aldehydes of this series are not very important, 



110 



OUTLINES OF ORGANIC CHEMISTRY 





, o 5-6- 




ALDEHYDES, KETONES, AND AMINES 111 

but some of them find use as perfumes. The odor is a less 
noticeable property of those members of the series contain- 
ing more than fourteen atoms of carbon. 

KETONES. 

The ketones are closely related to the aldehydes. Both 
contain the carbonyl group, but whereas in the aldehydes 
this is connected on one side to an alkyl radicle and on the 
other to hydrogen, in the ketones it is connected on both 
sides to alkyl radicles. As might be expected, the two 
classes of substances show many analogies in their methods 
of preparation and behavior: thus, while the aldehydes are 
formed by the oxidation of primary alcohols, ketones are 
formed by the oxidation of secondary alcohols: 

CH 3 CH 3 

>C( +0 = H 3 0+ )C = 0. 
CH 3 0H CH 3 

One of the most important methods for the preparation of 
ketones depends upon another reaction closely analogous to 
one employed for the preparation of aldehydes. It will be 
recalled that when calcium acetate is distilled with calcium 
formate, acetaldehyde is produced. Similarly when calcium 
acetate is distilled alone, calcium carbonate is formed and 
the simplest ketone, acetone, distills over: 

CH3 ~ C \ CH 3 

)Ca = CaC0 3 + ^C = 0. 

oh 

CH 3 - r / Lti * 

3 °^0 

The same reaction may also be applied to the preparation of 
what are called mixed ketones, that is, substances in which 



112 OUTLINES OF ORGANIC CHEMISTRY 

two dissimilar alkyl radicles are attached to the carbonyl 
group. If a mixture of calcium acetate and calcium pro- 
pionate be subjected to dry distillation, ethyl methyl ketone, 



CH 3 — CH 2 

)co, 

CH 3 

is formed, along with some acetone and some diethyl ketone. 
In chemical behavior, the ketones strongly resemble the 
aldehydes. Reduction yields secondary alcohols, while oxi- 
dation takes place with much more difficulty than with the 
aldehydes, because here oxidation involves a rupture of the 
carbon chain: 

CH 3 °H 3 

)C0 + 4 = CO + H 2 0+C0 2 
CH 3 QH 

This makes it plain why ketones do _jxok_act_as reducing 
agents. 

The ketones enter into addition and condensation reactions 
which are similar to those shown by the aldehydes, but since 
they have no hydrogen atom attached to the carbonyl 
group, they do not readily polymerize. 

Acetone or dimethyl ketone is the simplest and best known 
member of the series. It is found in pyroligneous acid, and 
may be obtained thence after the acetic acid has been 
removed by treatment with lime, and the methyl alcohol has 
been combined with calcium chloride or oxalic acid. Much 
of the crude calcium acetate formed in the same process is 
also distilled with superheated steam for the preparation of 
acetone. The yield by this method is good, but the product 
contains some of the higher homologues, notably ethyl methyl 
ketone. 



ALDEHYDES, KETONES, AND AMINES 113 

Acetone is a colorless liquid of a peculiar, not disagreeable 
odor and burning taste. It boils at 57°, and is miscible in 
all proportions with water as well as with alcohol and ether. 
Like alcohol, it can be separated from its aqueous solution 
by means of potassium carbonate. It finds extensive use 
as a solvent, as well as in the preparation of chloroform, 
iodoform, and sulfonal. It is also used for gelatinizing nitro- 
cellulose in the preparation of smokeless powder and allied 
products. 

In the preparation of chloroform, acetone is treated with 
a mixture of bleaching powder and water, and the mixture 
is distilled. The chloroform settles out as a heavy oily 
liquid at the bottom of the distillate. The mechanism of the 
reaction is regarded as consisting in a chlorination of the 
acetone to form trichloracetone, CH 3 — CO — CC1 3 , which 
then splits under the action of the lime in the bleaching 
powder, yielding chloroform and calcium acetate: 

;C-CH 3 

o 

2 CH 3 - CO - CCI3 + Ca(OH) 2 = Ca ( +2 CHC1 3 . 

O 

C-CH 3 

Ethyl alcohol may also be used as a starting point in the 

preparation of chloroform. In this case trichloracetalde- 

hyde, more commonly known as " chloral," 

CC1 3 

I , 
CHO 

is an intermediate product. When it is desired to isolate 

this compound, chlorine gas is led directly into ethyl 

alcohol. If water is present, chloral unites with it to form 

a crystalline addition product known as " chloral hydrate," 



114 OUTLINES OF ORGANIC CHEMISTRY 

This is used in medicine as a hypnotic. When boiled with 
alkalies, chloral yields chloroform and an alkaline formate: 

CC1 3 H P1 

I ,0 |0 / U 

Cf +KOH = Cf +HC-C1. 
X H. X 0K \ C1 

Chloroform is a heavy, colorless liquid of a rather sweetish, 
agreeable odor. It boils at 61°, and has the specific gravity 
1 .5. Owing to its high chlorine content, it is not inflammable. 
The use of chloroform as an anaesthetic is well known. It was 
first employed in surgery for this purpose by Simpson in 
Edinburgh in 1847. 

The preparation of iodoform depends upon a series of reac- 
tions entirely similar to those which take place when chloro- 
form is prepared from alcohol or acetone. Ethyl alcohol is 
treated with iodine and caustic potash, and the mixture 
gently warmed. The product is a yellow, crystalline solid. 
It has a characteristic odor and melts at 120°. It is used 
in dressing wounds. The formation of iodoform by the 
method above outlined makes a delicate and convenient test 
for the presence of ethyl alcohol or of acetone. Some other 
substances, however, show the reaction. 

THE AMINES. 

There are several distinct classes of organic compounds 
which contain nitrogen. Of these, one class, the nit riles, 
of the general formula RCN, has already received some 
attention. Another important class is that of the amines 
or substituted ammonias. These are the most important and 
best known of the organic bases. Most of the amines of 
technical importance belong to the aromatic members of 
the group, but several things of interest can be learned by 
a study of the aliphatic representatives. 



ALDEHYDES, KETONES, AND AMINES 115 

If ammonia be treated with an alkyl halide, such as methyl 
iodide, one, two or three of the hydrogens of ammonia may 
be substituted by an alkyl group in the sense of the follow- 
ing equations : — 

/CH 3 
NH 3 + CH 3 I =N-H +HI, 
N H 

/CH3 
NH 3 + 2CH 3 I==N-CH 3 + 2HI, 
X H 

/CH 3 
NH 3 +3CH 3 I = N-CH 3 + 3HI. 
X CH 3 

The products are called respectively primary, secondary, and 
tertiary amines. The first class is characterized by the grouping 

R - NH 2 , the second by NH and the third by R - N . 

The amines of lower molecular weight are gases at ordinary 
temperature. They have the odor of ammonia, and closely 
resemble that substance in physical and chemical properties. 
This is particularly well illustrated in the matter of salt- 
formation. If the gases, hydrochloric acid and ammonia, 
come together in the atmosphere, addition takes place and 
solid ammonium chloride is formed: 

Hx g\ 

H-N + HC1 = „>N-C1. 



116 OUTLINES OF ORGANIC CHEMISTRY 

The amines act in precisely the same way. They also add 
acids: nTT H v 

H - N + HC1 = „ 3 > N - CI , 

and the salts formed are substituted ammonium salts, hav- 
ing properties closely resembling those of the latter; thus 
they are crystalline solids, soluble in water, and their solu- 
tions conduct the electric current. It would be appropriate 
for these reasons that the compounds whose formulae follow: 

H \ H \ H \ 

g>N-Cl, C g >N-C1, and £j** 8 >N-Cl, 

CH 3 CH 3 CH 3 

should be named methyl ammonium chloride, dimethyl 
ammonium chloride, and trimethyl ammonium chloride re- 
spectively. Unfortunately a long historical usage has for- 
mulated them as double compounds, thus: — CHgTNPH^HCl, 
(CH 3 ) 2 NH,HC1, and (CH 3 ) 3 N,HC1; and given them the names, 
methylamine hydrochloride, dimethylamine hydrochloride, 
and trimethylamine hydrochloride respectively. We meet 
in these compounds the first representatives of the organic 
salts, while the amines themselves are the most typical 
organic bases. 

The salts resemble ammonium chloride in the manner of 
their decomposition as well as in their formation. When 
ammonium chloride is heated with alkalies, the ammonium 
hydroxide first formed is at once decomposed into am- 
monia, gas and water: 

NH 4 C1 + KOH = KC1 + NH 4 OH = KC1 + NH 3 4- H a O. 
Similarly, if methylamine hydrochloride is heated with alkali, 
decomposition takes place into water and methylamine: 

H \ PH 

5>NCl + KOH = KC1 + CH 3 NH S + H,0. 
CH,/ 



ALDEHYDES, KETONES, AND AMINES 117 

The amines have not only the capacity for adding acids. 
They also add the alkyl halides, thus trimethylamine can 
add methyl iodide as indicated by the following equation : 

pit CH 3 y 

CH 3 - N + CH 3 - 1 = pS 3 >N - I . 
CHV eg/ 

The product bears the appropriate name, tetramethyl 
ammonium iodide. This substance differs slightly in its 
chemical behavior from the salts just mentioned, but it 
shows only those differences which might be expected from 
its formula. Its salts are not decomposed by alkalies, but 
if they are treated with moist silver oxide, insoluble silver 
iodide is precipitated, and the solution contains the free 
base, tetramethyl ammonium hydroxide: 

CH 3 s^ CH 3 ^ 

2 £|[ 3>N ~ l + A &° + H 2° = 2 CH >N ~° H + 2 AgI * 
3 . 3 • 

CH 3 / CH/ 

It is obvious that this base cannot decompose as ammonium 
hydroxide does, because there is, in this case, no hydrogen 
attached directly to the nitrogen which might split off to 
form water. It accordingly remains undecomposed in solu- 
tion. If heated for itself, however, the base does decom- 
pose into trimethyl amine and methyl alcohol: 

CH 3 V pTT 

PIT UrL 3 \ 

p£ 3 > N - OH = CH 3 - N + CH 3 - OH . 

m\/ UJT CH3/ 

This is the closest analogy to the behavior of ammonium 
hydroxide which its structure permits. Substances of this 
type, or quaternary bases as they are called, are comparable 
in strength to the hydroxides of the alkali metals. It has 
just been stated that their salts are not decomposed by the 



118 OUTLINES OF ORGANIC CHEMISTRY 

latter. Other points of resemblance are the caustic action 
which they exert upon the skin, and the readiness with 
which they absorb carbon dioxide from the air to form 
carbonates. 

The reaction between ammonia and the alkyl halides leads 
to the formation of all three kinds of amines as well as the 
ammonium bases just mentioned, and the isolation of each 
component in such a mixture is a chemical operation of no 
little difficulty. As the primary amines are rather more 
important for us than any of the other classes, it is fortunate 
that there are several methods which lead to the formation 
of this class unmixed with representatives of the other types. 

One of these methods consists in the reduction of the ni- 
triles. When these substances are treated with zinc and 
hydrochloric acid, or better with sodium and alcohol, primary 
amines are formed in accordance with the following equation, 

CH 3 .CH 2 .C : N + H 4 = CH 3 .CH 2 .CH 2 .NH 2 . 

Another method of preparation is important on several 
grounds. This starts from the amides of those acids which 
contain one more atom of carbon than the amines in question. 
When the amides are treated with bromine and caustic 
potash, a complicated series of reactions takes place. The 
net result is the elimination of the carbonyl group from the 
amide, and the operation can be summed up in the following 
equation : 

.0 



NH 2 



CH 3 - CH 2 - C;_ w + Br 2 + 4KOH = 



XT 

CH 3 -C\ 2 +2KBr + K 2 C0 3 +2H 2 0. 
NH 2 

This reaction is particularly important as a step in passing 
from one acid of the fatty series to another having one less 
carbon atom. In the case of those acids containing more 



ALDEHYDES, KETONES, AND AMINES 119 

than five atoms of carbon, the reaction results in the forma- 
tion of the lower nitrile instead of the amine. This makes 
an even more convenient method for preparing one acid from 
the next higher: 

(1) R-CH 2 -C( +Br 4 + 6KOH = 

2 X NH 2 

R-CN + 4KBr + K 2 C0 3 -f4H 2 0; 

(2) R-CN + 2H 2 = R-COOH + 2NH 3 . 

Among the reactions of the amines, that of salt-formation 
has been already mentioned. There is another reaction 
which is not only important in its application to primary 
amines, but by its aid it is possible to distinguish the several 
classes from each other. This reaction is the one with 
nitrous acid. It will be recalled that ammonium nitrite 
is not a very stable compound, and that even upon boiling 
its aqueous solution, it breaks up into nitrogen and water; 
in fact this is a convenient laboratory method for the prepara- 
tion of nitrogen: 

NH 4 N0 2 = 2H 2 + N 2 . 

Primary amines, when treated with nitrous acid, behave 
in ~aiT analogous manner. Nitrogen gas is formed and one 
molecule of water, but instead of the second molecule, a 
substituted water, that is, an alcohol, is produced: 

C 2 H 5 - NH 2 + HN0 2 = H 2 + N 2 + C 2 H 5 - OH . 
This replacement of the amino-group, NH 2 , by hydroxyl is 
closely associated with some other chemical reactions of 
great theoretical as well as technical importance which will 
be studied later. Here it should be added that secondary 
amines do not react in a similar way with nitrous acid. 
Instead, substances called nitrosamines are formed in accord- 
ance with the following equation : 

CH 3 v CH 3 v 

/NH + HONO = H 2 +_ 7 N-N0. 

UJtia bH 3 



120 OUTLINES OF ORGANIC CHEMISTRY 

Finally, the tertiary amines have no hydrogen which is 
directly connected to nitrogen, and, apparently in con- 
sequence of this fact, do not react with nitrous acid. 

Individual Amines. Methylamine, dimethylamine, and 
trimethylamine are all gases at ordinary temperature. 
They resemble ammonia in their odor and their solubility 
in water. What has been said of their odor refers to the 
odor of the gases or highly concentrated solutions. In 
high dilution, the odor of ammonia becomes associated with 
an odor of decaying fish, and in such material several sub- 
stances of this class occur. The methylamines differ from 
ammonia in the fact that they are combustible. The ethyl- 
amines are volatile liquids of similar properties. 



THE ACID AMIDES. 

These substances have already received brief consideration 
in connection with the other acid derivatives. Here it is 
only desired to point out the analogies which exist between 
them and the amines. They differ from the latter in having 
the hydrogen of ammonia replaced by an acyi (page 93) 
instead of an alkyl radicle. The negative character of the 
acyl group may be regarded as compensating the basic 
nature of ammonia, and, as a result, the amides are practi- 
cally neutral substances. Secondary and tertiary amides 



having such formulae as 
i 
NH and (RCO) 3 N 



R-CO 
\ 
/ 

R-CO 



are known, but are rare and unimportant as compared with 
the primary compounds. The latter show the same reaction 
with nitrous acid as the primary amines, and this affords 



ALDEHYDES, KETONES, AND AMINES 



121 



o 2 w H.s 

8 ^-HHo^H^-a wo! 

Y | > 7 o-o-o a 




122 



OUTLINES OF ORGANIC CHEMISTRY 



k 




ALDEHYDES, KETONES, AND AMINES 



123 




124 OUTLINES OF ORGANIC CHEMISTRY 

an additional means of passing from the amides to the 
corresponding acids: 

(1) CH 3 -CONH 2 + KOH = CH 3 -COOK + NH 3 . 

(2) CH 3 -CONH 2 + HN0 2 = H 2 + N 2 + CH 3 -COOH. 

Relations between the Fatty Acids and their Deriv- 
atives. Upon the preceding page will be found a scheme 
representing, among other things, methods of passing from 
acetic acid to propionic acid and back again. It indicates 
most of the more important genetic relationships which 
obtain between the various classes of substances hitherto 
studied, and the operations referred to are, for the most part, 
of general application, coordinating a good deal of valuable 
information. 

It should be added that the constitution of substances 
belonging to the higher series is usually established by 
connecting them, through some of the reactions here indi- 
cated, with other compounds of known constitution. 



CHAPTER VI. 

UNSATURATED COMPOUNDS. 

Ethylene. When ethyl iodide is treated with potassium 
hydroxide in alcoholic solution, the following reaction takes 
place : 

CH 3 CH 2 

I + KOH = KI + H 2 + II • 
CH 2 I CH 2 

The product, whose constitution will be discussed later, is 
called ethylene. It is a colorless gas of a sweetish odor 
which burns with a flame more luminous than that of meth- 
ane. Ethylene makes up about 2% of ordinary coal gas, 
and the latter owes much of its luminosity to the presence 
of this constituent. Ethylene is usually prepared in the 
laboratory by the action of sulphuric acid on alcohol, the 
sulphuric acid being kept in excess. The reaction is essen- 
tially a dehydration of ethyl alcohol: 





CH 3 
1 
CH 2 


= H 3 + 


CH 2 

II 
CH 2 



OH 

In its chemical properties, this gas differs in an important 
respect from the hydrocarbons previously studied. When 
ethane, for example, is treated with chlorine, the following 
familiar reaction occurs : 

CH 3 CH 3 

I + Cl 2 = HC1 + I 
CH 3 CH 2 C1 

125 



126 OUTLINES OF ORGANIC CHEMISTRY 

In the case of ethylene, however, no substitution occurs but 
addition: " ^ ^ 

II + CI, = I 
CH 2 CH 2 C1 

Ethylene chloride, the product of this reaction, is a heavy 
oil, and the chemists who first studied this reaction were 
so much impressed by the formation of an oil by the union 
of two gases, that they gave to ethylene the name, "ole- 
fiant " or oil-forming gas. The term olefine is still retained 
as a class designation for ethylene and its homologues. 

Chlorine is not the only substance added by ethylene. 
It also unites directly with quite a number of others. Here 
will be mentioned only its union with bromine to form 
ethylene bromide, with hydrobromic acid to form ethyl 
bromide, and with sulphuric acid in the cold to form ethyl 
sulphuric acid: 

CH 2 HO x CH 3 - CH 2 - O x 

II + S0 2 = S0 2 . 

CH 2 HO x HO/ 

By reduction in hydrogen ethane may be obtained: 
CH 2 CH 3 

II + H 2 = | • 
CH 2 CH 3 

Since ethylene adds so many substances directly, it is 
evident that its carbon atoms cannot be utilizing their full 
combining capacity, that is, they are unsaturated. This 
might find expression in one of the three following graphic 

f ormulae : 

H H 

H I I 

H\ I / H-C- H-C 

I. H- C - C x II. I III. II • 

H/ H-C- H-C 

I I 

H H 



UNSATURATED COMPOUNDS 127 

Formula I can be excluded by the following reasoning: — 
A hydrocarbon of that formula, when treated with chlorine, 
should yield a chloride of the formula, 

Now a substance having this formula is known, and its 
constitution is rendered certain by the fact that it can be 
prepared from acetaldehyde by the action of phosphorus 
pentachloride: 

TT H TT H 

H \ I H \ I /CI 

H- C - C = O + PC1 5 = POCI3+ H-C - C( > 
H / H / CI 

while it yields acetaldehyde again when it is treated with 
hydrolytic agents. This compound, however, is not identi- 
cal with that which is formed by the addition of chlorine to 
ethylene. The latter must then have the only other formula 
possible, namely, jj 

I 
H - C - CI 

I 
H - C - CI 

I 

H 

and this is in harmony with either formula II or III for 
ethylene. It is not quite so easy to reach a decision be- 
tween these two, but III is universally preferred to II for 
the following reasons : — If carbon valencies could exist free 
in the sense of II, then there would seem to be no good reason 
why they might not .exist alone. It might be expected that 
such compounds as 

/H /CH 3 

methyl, -C-H, or tertiary butyl, — C— CH 3 , 

N H N CH 3 



128 OUTLINES OF ORGANIC CHEMISTRY 

might exist as compounds. All attempts to prepare sub- 
stances of this type have, however, been uniformly unsuccess- 
ful. It is always the case that molecules of unsaturated 
compounds add an even number of atoms of other sub- 
stances, and study of the products reveals the fact that 
addition, except in a few cases otherwise well accounted 
for, takes place upon two adjacent carbon atoms. The 
quality of unsaturation manifested by ethylene is then a 
relationship existing between adjacent carbon atoms, and 
hence this relation is better expressed by the formula, 



H- 


- C - H H 2 = C 




II than by | 


H- 


-C-H H 2 =C 



An important reaction of ethylene and other substances 
possessing a double bond is their behavior upon oxidation. 
This also may be looked upon as an addition reaction. 
The aqueous solution of an oxidizing agent may be regarded 
as a mixture of nascent oxygen and water. If an olefine 
is present, these react with it in such a way that a hydroxyl 
group is added to each carbon atom adjacent to the double 
bond. Further oxidation then leads to rupture of the carbon 
chain, usually resulting in the formation of acids. These 
operations are indicated in the following scheme: 

CH 3 CH 3 CH 3 

I I I 

CH HC - OH CO . OH 

II I + 

CH > HC-OH > CO- OH- 

I I I 

CH 2 CH 2 CH 2 

I I I 

CH 3 CH 3 CH 3 

It will be noted that the chain is broken at the point 
originally occupied by the double bond. In practice, it is 



UNSATURATED COMPOUNDS 129 

by oxidation reactions of this sort that the position of the 
double bond in an unsaturated compound of unknown con- 
stitution is usually determined. 

The homologues of ethylene can be most conveniently named 
as alkyl derivatives of ethylene itself thus : CH 3 — CH = CH 2 
methylethylene, CH 3 - CH 2 - CH = CH 2 ethylethylene, 
CH 3 - CH = CH = CH 2 - CH 3 methylethylethylene, etc. 
Other names are also in use which are formed by adding the 
syllable " ylene " to the root of the name of the saturated 
hydrocarbon having the same number of carbon atoms. 
For the compounds just mentioned, this method gives the 
names propylene, butylene, and amylene. 

Acetylene. If ethylene bromide be treated with alco- 
holic potash, two molecules of hydrobromic acid are removed, 
and acetylene is produced: 

H 2 = C - Br C - H 

I +2KOH = 2KBr + 2HX>+IH 

H 2 =C-Br C-H 

The triple bond in the formula indicates that it possesses 
another pair of unsatisfied valencies; indeed acetylene may 
be considered twice as unsaturated as ethylene. It unites 
directly, for example, with four atoms of chlorine or bromine 
instead of two. It has just been shown that upon oxida- 
tion the carbon chain of an olefine is broken at the double 
bond. This also holds true of the compounds of the acety- 
lene series, and in addition, the triple bond seems to be the 
cause of general instability. Acetylene itself is not indeed 
explosive under ordinary conditions, but it becomes so when 
subjected to high pressure, and it has many explosive deriv- 
atives. The triple bond has another peculiarity. Hydro- 
gen connected to carbon atoms united by such a bond may 
be replaced by heavy metals such as silver or copper, and 
the compounds thus formed are explosive. Such a product 



130 OUTLINES OF ORGANIC CHEMISTRY 

is precipitated when acetylene, for example, is passed 
through an ammoniacal solution of cuprous chloride: 

C - H Cu - C 

III + Cu 2 Cl 2 + 2 NH 4 OH =| HI + 2 NH 4 C1 + 2 H 2 . 

C - H Cu - C 

Such compounds are readily decomposed by dilute acids, the 
hydrocarbons being regenerated: 

Cu - C C - H 

I |||+2HCl=Cu 2 Cl 2 +IH 
Cu - C C - H 

The formation of these explosive metallic compounds is 
characteristic of substances containing a triple bond, and 
furnishes a convenient means of distinguishing them from 
the isomeric compounds containing two double bonds. 

Acetylene itself is usually prepared in practice by the 
action of water upon calcium carbide: 

OH C-H 

Ca'lH + 2H 2 = Ca' + ||| 
X C X OH C-H 

The latter compound, which was considered a chemical 
curiosity a few years ago, is now manufactured upon a large 
scale by heating coke and lime to the high temperature of 
the electric furnace: 

CaO + 3C = Ca'||| + CO . 
X C 

Calcium carbide is a hard, black solid which is immedi- 
ately decomposed by water, yielding acetylene and lime. 
The product obtained in this way is by no means pure. On 
account of impurities in the crude carbide, it usually contains 
hydrogen sulphide, ammonia, some phosphine, and some 
organic sulphur and phosphorus compounds. From these it 
can be largely freed by passing through lime and some oxi- 
dizing material, such as bleaching powder or one of the chro- 



UNSATURATED COMPOUNDS 131 

mates. When an especially pure gas is desired, it can be 
prepared by passing the acetylene through an ammoniacal 
solution of cuprous chloride, and then decomposing the result- 
ing copper compound by means of dilute acids or potassium 
cyanide. 

Acetylene is produced to some extent in the flame of a 
" struck back " Bunsen burner. Its presence in the gases 
issuing from such a flame may be shown by conducting 
them through an ammoniacal copper solution. Still another 
method of formation is of scientific interest. When the 
electric arc passes between carbon terminals in an atmos- 
phere of hydrogen, the carbon and hydrogen react until 
an equilibrium is reached. At this point the gases present 
are in the following proportions: — Hydrogen 90-91%, 
Acetylene 7-8 %, Methane 1.25 %, Ethane- 0.75 %. 

Acetylene is a colorless gas of a characteristic odor. When 
ignited in the air, it burns with a heavy deposition of soot 
owing to the extremely high percentage of carbon which 
it contains. By means of a specially constructed jet-piece, 
however, it is possible to obtain the brilliant illuminating 
effect familiar in the acetylene search-light. Acetylene can 
hardly be considered an altogether safe illuminant, as, aside 
from its becoming less stable under pressure, it has two 
other disagreeable properties. One is its capacity for form- 
ing explosive metallic compounds, and the other is the fact 
that mixtures of it with oxygen or air are explosive through- 
out a wide range of percentage composition. For purposes 
of transportation acetylene may be conveniently and safely 
dissolved in acetone under pressure. Numerous homologues 
of acetylene are known. 

The property of unsaturation is by no means confined 
to hydrocarbons. All classes of organic compounds may 
exhibit it. There are unsaturated alcohols like allyl alcohol, 
CH 2 = CH-jCH 2 OH, unsaturated aldehydes like acrolein, 



132 



OUTLINES OF ORGANIC CHEMISTRY 




UNSATURATED COMPOUNDS 133 

CH 2 = CH — CHO, and numerous unsaturated acids. One of 
these, oleic acid, should be mentioned at this time. It is 
important l3ecause of its occurrence as an ester in the natural 
fats. Oleic acid is an oily liquid insoluble in water. Under 
ordinary pressure, it does not distill without decomposition. 
It has the same number of carbon atoms as stearic acid, 
into which it is readily transformed on reduction. It there- 
fore differs from the latter only in the possession of a double 
bond. The position of the double bond was for a long time 
in doubt, but recent investigation makes it certain that 
this is found just in the middle of the chain. The structural 
formula of oleic acid is, therefore, the following: — 

CH 3 - (CH 2 ) 7 - CH = CH - (CH 2 ) 7 - COOH. 



CHAPTER VII. 

THE POLYATOMIC ALCOHOLS AND THEIR DERIVATIVES. 

It has been shown in the preceding pages that each of 
the important groups of organic compounds is characterized 
by the possession of some particular group or radicle to 
which it owes its especial properties. The alcohols are 
characterized by the hydroxyl group, the aldehydes by 
carbonyl, the acids by carboxyl, and so forth. Now it is 
true of almost all of the compounds hitherto studied that 
they contain this characteristic group or radicle but once. 
The alcohols thus far met with were those containing but 
one hydroxyl group, the acids were those having but one 
carboxyl. Now there is, of course, no limitation of this 
sort in nature. On the contrary, many alcohols exist 
containing several hydroxyl groups (polyatomic alcohols), 
acids with several carboxyl groups (polybasic acids) and 
the same is true of other classes of compounds. Further, 
it is possible for one and the same substance to contain 
several different radicles, and compounds may exist which 
are, for example, amines, alcohols, and acids all at the same 
time. Fortunately the study of such compounds does not 
involve much which is new in principle, since the different 
radicles each contribute their properties to the compound 
in a manner which is roughly additive. Nevertheless the 
specific properties of particular groups are not infrequently 
a good deal modified by the simultaneous presence of others. 

It is convenient to begin our study of these more complex 
substances with the polyatomic alcohols. It should be 
stated at the outset that the term atomicity as applied 

134 



POLYATOMIC ALCOHOLS 135 

to an alcohol is intended to designate the number of its 
hydroxyl groups. The alcohols previously studied have 
been monatomic alcohols, since they contained but one 
such group. There remain to be considered the diatomic, 
triatomic, and higher compounds collectively known as poly- 
atomic alcohols. The number of these is a good deal cur- 
tailed by the fact that only in exceptional cases is it possible 
for two hydroxyl groups to remain attached to the same 
carbon atom. The simplest possible diatomic alcohol is 
therefore the substance known as glycol, having the formula, 

H 2 C - OH 

I 
H 2 C - OH 

The constitution is obvious from the reactions by which it 
may be prepared from ethylene bromide. When that sub- 
stance is treated with potassium acetate for some time, the 
bromine atoms are both replaced by acetic acid radicles, 
and when this acetate is then saponified, glycol is produced: 

O 
II 
CH 2 Br CH 2 -0-C-CH 3 

I +2KC 2 H 3 2 = 2KBr+ I ; 

CH 2 Br CH 2 -0-C-CH 3 

II 
O 

o 

II 

CH 2 -0-C-CH 3 CH 2 OH 

I + 2H 2 = 2CH 3 -C00H + I 

CH 3 -0-C-CH 3 CH 2 OH 

II 
O 

It is a colorless liquid which is miscible with water in all 
proportions. These properties, together with the sweet 



136 



OUTLINES OF ORGANIC CHEMISTRY 



taste, from which glycol derives its name (Greek yAvic.vs, 
sweet) are common to the polyatomic alcohols. The more 
important chemical properties of glycol can be derived 
directly from the formula. This shows the substance to 
be twice a primary alcohol. Hence it is possible to predict 
that either one or two of its hydrogen atoms may be sub- 
stituted by sodium, that one or both hydroxyl groups may 
be substituted by chlorine or bromine, and that the sub- 
stance may unite with one or two molecules of acids to form 
esters. Under the influence of oxidizing agents, it is clear 
that a considerable number of different compounds might 
be produced according to whether one or both of the hy- 
droxyl groups undergo oxidation. These possibilities are 
indicated in the following scheme: 



CH 2 -OH^ 
CH 2 - OH 

Glycol 





c = o x 






CH 2 - OH 

1 /^ 


1 \ 
, C = 

^ X H 


^ c=o 


y 0H 

c=-o 


C-0 ' 
X H \ 

Glycol 
aldehyde 


Glyoxal 
CH 2 OH y 

N C = 
N 0H 

Glycolic 


» c = o 

X 0H 

Glyoxylic 
acid 


1 

C = 

X 0H 

Oxalic 
acid 



All the above compounds are known, though most of them 
have little practical importance. An exception is the final 
product, oxalic acid. This substance is of especial im- 
portance, not only on its own account, but also because it 
is a typical representative of the dibasic acids. Two methods 
of preparation deserve mention for their scientific interest. 
One consists in the series of operations indicated above: 
the other involves the hydrolysis of cyanogen: 



POLYATOMIC ALCOHOLS v 137 

ONH 4 

/ 
CN C = O 

I +4H 2 0= I 
CN C = 

ONH 4 

This reaction exhibits cyanogen as the nitrile of oxalic acid. 
The acid derives its name from the sorrel (oxalis acetosella), 
in which it occurs in nature, as well as in rhubarb and some 
other plants. In practice, it may be prepared by the oxida- 
tion of numerous organic substances. One of the most con- 
venient methods of laboratory preparation upon the small 
scale is the vigorous oxidation of cane sugar by means of nitric 
acid. For technical purposes, the salts may be obtained 
by heating the formates to about 450° with exclusion of air: 

ONa 

/ 
ONa C = 

2H-C( =H 2 + | 

^O C = 

\ 
ONa 

The more usual method of technical production consists in 
the fusion of sawdust with a mixture of sodium and potas- 
sium hydroxides at a temperature of about 220°. Hydrogen 
gas is evolved during the operation. The melt is first 
leached out with water, the solution containing a mixture 
of sodium and potassium oxalates along with other soluble 
impurities. From this solution, the addition of lime pre- 
cipitates insoluble calcium oxalate, which may then be 
purified and decomposed with the calculated quantity of 
dilute sulphuric acid. Insoluble calcium sulphate is pro- 
duced, while oxalic acid remains dissolved. Upon evapora- 
tion, this crystallizes from the solution with two molecules 



138 OUTLINES OF ORGANIC CHEMISTRY 

of water. By careful heating, the water of crystallization 
can be removed without decomposing the compound. The 
anhydrous acid may then be sublimed at about 150°, but 
on rapid heating it decomposes, partly into carbon mon- 
oxide, carbon dioxide, and water, and partly into carbon 
dioxide and formic acid: 

OH 

(1) C=0 

I = H 2 + CO + C0 2 . 

C=0 
\ 
OH 

OH 
/ H 

(2) C = O I 

I = CO + co 2 . 

C = \ 

\ OH 

OH 

Heating with concentrated sulphuric acid favors the de- 
composition indicated by the first equation, and this is one 
of the most convenient laboratory methods for the prepara- 
tion of carbon monoxide. Heating the anhydrous acid with 
pure glycerin causes decomposition in the sense of the 
second equation. Formic acid is usually prepared in the 
laboratory by this method. Oxalic acid and, its salts, when 
treated with permanganates in acid solution, are smoothly 
oxidized to water and carbon dioxide: 

COOH 

5 I +2KMn0 4 +3H 2 S0 4 =K 2 S0 4 +2MnS0 4 -f 10CO 2 +8H 2 O. 

COOH 

Extensive use is made of this reaction in volumetric analysis. 

On ignition, most oxalates lose carbon monoxide with 

formation of the corresponding carbonate, which may then 



POLYATOMIC ALCOHOLS 139 

lose carbon dioxide forming the oxide. This decomposition 
is so smooth that practically no charring takes place. It 
may be conveniently observed in the case of the calcium salt: 

o-c=o o 

Ca; I = CO + Ca' x CO; 

X 0-C=0 x O X 

Ca' X CO = C0 2 +CaO. 
X O x 

The insolubility of this compound makes it useful for the 
gravimetric determination of both calcium and oxalic acid. 

As already pointed out, oxalic acid may be considered as 
a type of the dibasic acids in general. Two other members 
of the series will, however, be mentioned. 

Malonic Acid. When acetic acid is treated with chlorine, 
a hydrogen atom in the methyl group is substituted by the 
halogen, forming, in this case, chloracetic acid: 



CH 3 /^ 
1 C = H 2 

e=o + ei 2 = HCL+ i 

x 0H C=0 
x OH 
When the latter is treated with potassium cyanide, 


the 


following reaction takes place: 

/ C1 

CH 2 / CN 
1 + KCN = KC1 + CH 2 
COOH x C0QH 

the product being the nitrile of malonic acid. From this, 


the acid itself may be formed 
/ CN 

CH 2 4- 2H 2 
X COOH 


. by hydrolysis: 

^COOH 

= NH 3 + CH 2 

x COOH 





140 OUTLINES OF ORGANIC CHEMISTRY 

Malonic acid is a crystalline solid. When heated above 
its melting point, it decomposes into carbon dioxide and 
acetic acid: 

/ C00H CH 3 

CH 2 =C0 2 + I 

N COOH C00H 

Behavior of this kind is common to substances containing 
two carboxyl groups attached to the same carbon atom. 
The ethyl ester of malonic acid is frequently employed in 
many syntheses which are very important for the profes- 
sional worker in Organic Chemistry. This matter will not, 
however, be discussed here. One reaction of general in- 
terest does deserve mention, as it leads to the formation 
of the recently discovered third oxide of carbon. When 
malonic acid is heated with phosphorus pentoxide, water is 
removed, and among other less well-defined products, a gas 
is evolved which probably has the constitution indicated in 
the reaction which follows: 



,OT 




/ C = 


,C-0 


CH 2 


= 2H 2 + C 


X C = 


^C = 


X 0H 





To this substance its discoverers have given the name 
carbon suboxide. It is a gas which may be readily con- 
densed to a liquid boiling at 7°. It has an intolerable odor 
suggestive of the acid anhydrides. Indeed it may be con- 
sidered as belonging to this class of substances, for with 
water it reacts readily, regenerating malonic acid. 

S uccinic. Acid . This acid has some important deriva- 
tives which wUlbe taken up later. It is a crystalline solid, 



POLYATOMIC ALCOHOLS 141 

soluble in water, and is technically prepared by the distilla- 
tion of amber, a source suggested by its name (Latin, suc- 
cinum, amber). The constitution of the acid is made obvi- 
ous by the synthesis indicated in the following scheme: 

OH 



CH 2 

1 


Br 


CH 2 

_> 1 


KCN 

> 


CN 

CH 2 

1 

CH 2 


H 2 


/ 
C = 

CH 2 

1 


CH 2 




CH 2 




CH 2 






X Br 




1 
CN 




1 

C = 



TRIATOMIC ALCOHOLS. GLYCERIN. 

The simplest of the triatomic alcohols is glycerin. It 
is a syrupy, hygroscopic liquid of sweet taste, which crystal- 
lizes at low temperature, and can only be distilled at ordinary 
pressure without decomposition when extremely pure. As 
its formula, 

CH 2 OH 

I 
CHOH , 

I 
CH 2 OH 

indicates, it is twice a primary and once a secondary alcohol. 
Glycerin is widely distributed in nature, since most animal 
fats and vegetable oils are glycerin esters of acids of the 
acetic acid series. These esters have a considerable practi- 
cal importance, and this gives to glycerin its chief interest. 
Before taking up their study, however, it is convenient to 
turn to one of the simpler inorganic esters, the trini trate.. 
This substance, commonly known as "nitroglycerin,'' is an 
important explosive. It is prepared by intimately mixing 



142 OUTLINES OF ORGANIC CHEMISTRY 

glycerin with nitric acid in the presence of sulphuric acid 
as a condensing agent: 

CH 2 OH H 2 C - ON0 2 

I I 

CHOH + 3HN0 3 = 3 H 2 + HC - ON0 2 . 
I I 

CH 2 OH H 2 C - ON0 2 

When action has ceased, the nitrating mixture is run off into 
a large quantity of cold water. The glycerin nitrate then 
separates as a heavy oil, which is thoroughly washed with 
water and finally dried. The product has a characteristic 
heavy odor and burning taste. Administered in extremely 
small doses, it has found some use in medicine. The pure 
liquid has proved somewhat unreliable as an explosive, and 
its use in this form has now practically ceased. It has been 
found that when the oil is absorbed in porous material like 
infusorial earth, a dry-feeling mixture results which is not 
sensitive to slight changes of temperature or to shock, but 
may be brought to explosion with certainty when " de- 
tonated " by a cap containing mercury fulminate. Under 
the name of " dynamite," such a mixture has come to be 
used extensively as a blasting material and is considered 
adequately safe. 



INDUSTRIES INVOLVING THE NATURAL FATS AND OILS. 

It has been pointed out above that the animal fats are 
the glycerin esters of acids of the acetic acid series. Those 
most commonly found in the animal organism are the esters 
of stearic, palmitic, and oleic acids. They are named stearin, 
palmitin, and olein, respectively. Like the free acids, stearin 
and palmitin are solids at ordinary temperature, while olein 
is a liquid. Olein predominates in a fat like lard, stearin 



POLYATOMIC ALCOHOLS 143 

in mutton tallow. From the earliest times, soaps have 
been prepared from the fats by treatment witn caustic 
alkali. When these are boiled together the esters undergo 
hydrolysis, a reaction occurring which is entirely analogous 
to that which takes place when a simple ester like ethyl 
acetate is treated with alkali: 

CH 3 CH 3 

I I 

C = + KOH = C = + C 2 H 5 OH. 

\ \ 

OC 2 H 5 OK 

The analogy between these two relations has led to the 
adoption of the word " saponification " to cover the whole 
class of reactions of this kind. In actual soap-making, the 
products are glycerin and the sodium salts of palmitic, 
stearic, and oleic acids. When the reaction is complete, salt 
is added to the solution and the soaps rise to the top, while 
the glycerin with the excess of alkali forms a lower layer. 
From this the glycerin may be obtained by evaporation 
and subsequent distillation. It need hardly be pointed out 
that, in early times, when the constitution of the fats was 
unknown, the glycerin, on account of its solubility in water, 
was overlooked entirely, and allowed to go to waste with 
the spent alkaline liquors. 

Another industry involving the saponification of the fats 
is the manufacture of stearin candles. These do not con- 
sist (as their name might imply) of true stearin, that is, 
glycerin stearate, but, instead, of the solid free fatty acids, 
mostly stearic and palmitic. The superiority of the stearin 
candle to the tallow candle has a chemical reason. When 
glycerin is heated, especially if in the presence of dehy- 
drating agents, an unsaturated aldehyde is formed named 
acrolein: . - 



144 OUTLINES OF ORGANIC CHEMISTRY 

H 2 C - OH CH 2 

I II 

H C - OH = 2 H 2 + CH . 

I I 

H 2 C - OH C = O 

H 

This substance attacks vigorously the mucous membrane 
of the nose and eyes, and its presence in small quantities is 
responsible for the disagreeable odor produced when fat is 
burned. The acids of which the stearin candle is composed 
are free from glycerin, and consequently do not produce the 
same disagreeable results. Technically the material for 
making these candles is usually obtained by heating the 
fats with a small amount of lime under pressure. The lime 
acts chiefly as a catalyzer, and the chief products of the 
reaction are glycerin and the free fatty acids along with a 
small amount of a calcium soap. The latter is then decom- 
posed with sulphuric acid. The fatty acids now float upon 
the top of the aqueous glycerin solution. This upper layer 
is run off and allowed to cool, when the stearic and palmitic 
acids mostly crystallize out. These are freed from the 
liquid oleic acid by means of mechanical pressure and the 
solid material is molded into candles. 

It should be added that the above is by no means the only 
source from which candles are obtained. Perhaps the most 
of the candies in use are made from paraffin, while others 
are prepared from many of the natural waxes, such as bees- 
wax, and from spermaceti, which is found in the head of the 
sperm whale. 

THE DRYING OILS. 

Allied to the fats in chemical composition is a class of 
substances known as drying oils. Of these, linseed oil, the oil 
found in the seeds of the flax, is the most conspicuous example. 
It is well known that this oil is the chief constituent of most 



POLYATOMIC ALCOHOLS 145 

paints and varnishes, and it is of interest to see how its chem- 
ical properties fit it for this use. Paint or varnish is applied 
to a wood or other surface chiefly to preserve the material 
from the action of the atmosphere. The object to be at- 
tained is a waterproof coating which shall be sufficiently 
elastic not to crack when dry. This may be realized in two 
ways. One of these, which may be called the mechanical 
method, is to dissolve a suitable gum or resin in a volatile 
solvent like alcohol or ether. When such a solution is 
spread upon a surface, the solvent evaporates, leaving a thin 
coat of the original gum or resin. A familiar example of 
this type is ordinary shellac. The other method is to employ 
a drying oil like linseed oil. When such an oil " dries," 
the drying is not due to the evaporation of any portion of it, 
but to oxidation. Linseed oil has the property of taking 
up oxygen from the air, and the product is an adhering solid 
material suitable for the protection of surfaces from the 
weather. This power of absorbing oxygen as exhibited by 
linseed oil is doubtless closely associated with the unsatu- 
rated character of its components. These are glycerin esters 
of oleic, linoleic, linolinic, and isolinolinic acids. Oleic acid 
has been already discussed (page 133). The other acids, like 
oleic, have the same carbon skeleton as stearic acid, but differ 
from this by their high degree of unsaturation. The free acids 
have only recently been prepared in a pure state, but, from 
a study of their derivatives, it is quite certain that linoleic 
acid contains two double bonds, while the two linolinic 
acids each contain three. 

All who have had to do with paints are familiar with the 
terms " raw " and " boiled " linseed oil. The latter term 
is applied to an oil which has been boiled for some time, 
usually with oxides of lead or manganese. Some of these 
bases are taken up by the oil, which becomes a good deal 
darker in color. It has also acquired the power of drying 



146 OUTLINES OF ORGANIC CHEMISTRY 

more rapidly. This has usually been ascribed to the cata- 
lytic action of the bases absorbed by the oil, but recent 
investigations seem to indicate that it is largely due to the 
partial oxidation effected during the process of boiling. The 
oxidation of linseed oil is an autocatalytic process, that is 
to say, the reaction is hastened by the presence in the oil 
of some of the oxidized product. An application of this 
principle has made it possible to use an oil which, instead 
of being boiled, has been partially oxidized at ordinary 
temperatures by agencies which do not affect the color. A 
light, very transparent varnish is the result. A word 
remains to be said concerning the function of turpentine 
in paints and varnishes. The theory is that pinene, the 
chief constituent of oil of turpentine, absorbs oxygen from 
the air, forming a substance of peroxide character, which 
acts as a particularly energetic oxidizing agent upon any 
oxidizable material which may be present, in this case the 
linseed oil. Other materials used as " driers " play a similar 
role. 

Before leaving the fats, it should be mentioned that they 
are used to a certain extent as a substitute for butter under 
the name of " oleomargarine." Butter itself is an allied 
substance. It consists of a mixture of glycerin esters of 
several of the lower acids of the acetic acid series. Promi- 
nent among these are butyric, caproic, caprylic, and capric 
acids, as well as palmitic and oleic. 



CHAPTER VIII. 

HYDROXY-ACIDS. OPTICAL ISOMERISM. 



LACTIC ACID. 

In the souring of milk, and in the fermentation of sugar 
under the influence of certain bacteria, lactic acid is pro- 
duced. The product obtained in this way is a syrupy 
liquid which retains a little water with great tenacity. A 
practically identical product can be obtained synthetically 
either by the action of alkalies upon chlorpropionic acid or 
by the hydrolysis of the addition product formed by the 
action of hydrocyanic acid upon acetaldehyde: 



CHc 



CH. 
I 

C = 
\ 



ci 







OH 

Propionic acid 

CH 3 

I 

c = o — 

Acetaldehyde 



CH 3 

I x ci 
c = o 

x OH 

a-Chlorpropionic acid 

CH 




CH, 



HCN 




CN 

Lactonitrile 



OH 

Lactic acid 



■ These syntheses would seem to put the constitution of the 
compound beyond question, but it is found that the substance 
has twice_the molecular weight indicated by the formula. 
Furthermore, it_has been found possible, by methods which 
will be described later, to split this~substance into two other 

-tt? — ' 



148 OUTLINES OF ORGANIC CHEMISTRY 

acids very similar to itself. Both of these acids seem to have 
the graphic formula just suggested, for they differ among 
themselves in respect to practically but one property. One 
of them, in solution, rotates the plane of polarized light to the 
right, the other, in the same concentration, rotates it an equal 
amount to the left. This relationship is not confined to the 
acids themselves but is shown in their salts and most other 
derivatives. If two such optically opposite compounds are 
mixed: in molecular proportions, the inactive substance 
obtained by synthetic" processes is regenerated. This fixes 
the nature of the latter as a loose molecular compound of 
the other two. It is further to be noted that this inactive 
compound differs more widely in properties from its com- 
ponents than they do from each other. The differences 
referred to concern such properties as solubility and crystal- 
line form. The chemical properties of all are practically 
identical. In the two active compounds we are confronted 
by the serious difficulty of two compounds which both seem 
to claim the same formula. Now inspection reveals the 
fact that this formula possesses a peculiarity which has 
hardly been met with in the substances studied hitherto. 
It will be noticed that the carbon atom marked with an 
asterisk is connected with four dissimilar radicles. One 
bond connects it to hydrogen, a second to methyl, a third 
to hydroXyl, and a fourth to carboxyl. Such a carbon is 
said to be asymmetric for reasons which will presently 
appear, and it is a fact of experience that of all the many 
optically active natural products whose constitution has 
been determined, the formula of each contains at least one 
such atom. This leads us to seek the explanation of the 
existence of the two active lactic acids in the presence of the 
asymmetric carbon atom, but even here the valence theory 
as developed up to this point fails to give us an explanation. 
It has been found possible to solve this problem and many 



HYDROXY-ACIDS 



149 




Fig. 10. 



others much more complicated by making an additional 
assumption, and seeking the c ause of the isomerism in the 
arrangement of the carbon valencies in -Space. 

Since these valencies appear to be all equal, the simplest 
and most natural assumption concerning their spacial 
arrangement would be that the bonds 
are so situated that the solid angles 
included between them are all equal. 
This would be the case if the bonds 
were thought of as extending outward 
from the center of the carbon atom 
toward the vertices of a regular circum- 
scribed tetrahedron. This relationship 
is represented in the accompanying 
diagram. For the study of such re- 
lationships, it is convenient to employ models consisting 
of a central sphere to represent the carbon atom and rods 
to represent the bonds. Then balls of different colors can 
be used to represent the various substituting elements or 
groups. Now if, in such a model, four spheres of one 
color be attached to each of the four " bonds," the figure 
formed will be of such a character that four planes of 
symmetry can be passed through it. For the purposes of 
this discussion, a plane of symmetry may be defined as a 
plane dividing an object in such a way that each half shall 
stand to the other as an object to its image in the mirror. 
If now. instead of four balls of the same color, three of one 
color and one of another be employed, it will be found that 
now only two planes of symmetry can be passed through the 
figure, and if two balls of one color and one of each of two 
others be used, but one plane of symmetry is possible. 
Finally, when all four bonds are attached to spheres of 
different colors, no plane of symmetry can be passed through 
the resulting figure. This justifies the use of the word 




150 OUTLINES OF ORGANIC CHEMISTRY 

" asymmetric " as applied to a carbon atom whose four 
bonds are satisfied by four different atoms or atomic groups. 
The student can easily verify these relations for himself by 
making a tetrahedron of pasteboard in the manner indicated 
below and marking differently the four corners. 

To construct a tetrahedron, draw an equilateral triangle, bisect 
each of the three sides, and connect the three middle 
points thus found. Finally cut out the large triangle 
and fold up the corners along the lines of the smaller 
inscribed one. Join the points at the top by a piece 
of fine wire or paste over with paper. With such 
models the simpler relations of space isomerism can 
Fig. 11. be studied almost as well as with the more expen- 
sive ones described above. 

Returning now to the consideration of the model possessing 
no plane of symmetry: — if two such models be constructed 
exactly alike, and then in one of them the position of two 
of the colored balls be exchanged, the resulting figures are 
no longer identical, and by no amount of turning can one 
be perfectly superimposed upon the other. There exists, 
however, a peculiar relationship between them. It is pos- 
sible to place them in several such relative positions that 
a plane of symmetry can be passed between them. Two 
geometrical figures which stand to each other in this rela- 
tion of object to mirror image, and yet are not identical, are 
said to be enantiomorphous. The relationship is similar to 
that of the right and left hands. As applied to these models 
it is shown in the accompanying figure. 

It will be noticed that the relationships existing between 
these models is admirably adapted to illustrate that which 
exists between the lactic acids. The two models are made 
up of the same components similarly arranged but differing 
only in what may be termed the direction of arrangement. 
This point may be brought out by the fact that if, in 
model I, it is desired to pass from a to b to c, it is nee- 



HYDROXY-ACIDS 



151 





Fig. 12. 



essary to go in the direction followed by the hands of a 
watch, whereas the same requirement can only be fulfilled in 
model II by proceeding in the opposite direction. In the 
lactic acids, also, the closest similarity exists in all chemical 
and physical properties, with the important difference that 
the two acids rotate the plane of polarized light equally 
in opposite directions. Isomerism of this type is of common 
occurrence, and because it can be so well illustrated by the 
structure of the molecule as represented in three dimensions 
it has received the name of space- or stereo -isomerism (Greek, 
orepeos, cubic). The term, optical isomerism, is also applied 
to the special kind of space isomerism we are now studying, 
as the more general term also includes certain types of com- 
pounds not optically active. 

Substances like the lactic acids whose differences are to 
be explained by the presence of asymmetric carbon atoms 
are said to possess the same constitution but different 
" configurations" In the case of lactic acid, it is customary 
to distinguish that acid which rotates the plane of polarized 
light to the right by the prefix d- (dextrorotatory) and its 
optical opposite by the prefix I- (lsevo rotatory) . It should be 
stated at the outset that the prefixes d- and I- are not now 



152 OUTLINES OF ORGANIC CHEMISTRY 

used to indicate the direction in which a specific compound 
rotates the plane of polarized light. Instead, a prominent 
dextrorotatory compound in a given group is selected as a 
standard and all other members of the group which stand in 
a genetic relationship to this substance receive the prefix d- 
while to the optical opposites of these compounds is given the 
prefix 1-. The attempt is now being made to refer the con- 
figuration of all optically active substances to d-glucose, one of 
the carbohydrates. The convenience of such an arbitrary 
standard will be more apparent as we proceed. The prin- 
ciple involved can, however, be made clear from the follow- 
ing simple case. Let it be supposed that a given acid rotates 
the plane of polarized light to the right, while its ethyl ester 
(as might well be the case) rotates to the left. It is obvious 
that it is more important that the nomenclature employed 
should show the relationship of the acid to its ester, than 
that it should record the specific action of either upon the 
plane of polarized light. 

At this point the question naturally arises : — which of the 
models referred to on page 151 is to be considered as repre- 
senting d- and which Z-lactic acid? Since the relations be- 
tween all the components are the same in both except in 
the matter of direction, it is impossible to answer this ques- 
tion in the form stated. It can only be said that if one be 
arbitrarily selected to represent the first form, then the other 
represents the second. It is the same with representations 
made upon the plane of the paper. Such are necessary for 
convenience of discussion, and for this purpose a purely 
arbitrary system is employed. The model is held in such 
a position that the longest possible chain of carbon atoms 
shall be projected upon the paper as a vertical line. Then 
the other elements or groups are projected directly as side 
arms or branches. For the lactic acids, formulae like the 
following are thus obtained. Such projection reproduces 



HYDROXY-ACIDS 153 

somewhat inadequately the geometrical relationship between 
the models. 

CH 3 CH 3 

I I 

I. H - C - OH II. HO - C - H . 

I I 

COOH COOH 

When d- and Mactic acids are mixed in equal quantities, 
an optically inactive compound results which has double 
the molecular weight of the components. Its name is 
written dMactic acid. Compounds of this type are usually 
formed when t wo opt ical oppositesarejnixed, and they are 
designated as r acemic com pounds. The name comes from 
racemic acid, the first substance of this type to be studied. 
It is closely allied to tartaric acid. 

When the attempt is made to synthesize in the laboratory 
any substance containing asymmetric carbon atoms, in- 
active products are always first obtained, and it is necessary 
to " split " these in order to obtain the optically active 
substances. The latter are usually formed directly by the 
plant or animal organism. That the racemic form should 
be the first product of artificial synthesis is entirely in line 
with what might be expected of isomers of this type, for 
since the kind and arrangement of the atoms are the same in 
the molecules of both isomers, both must have the same 
energy content, and as the chances of formation of each 
form are equal, both will be formed by any synthesis in 
equal quantities. Why it is that the syntheses going on 
in plant and animal organisms proceed unsymmetrically is 
one of the fascinating unsolved problems of Physiological 
Chemistry. 

From what has been said, it will be seen that the " split- 
ting" of racemic compounds is an important laboratory 
operation, but before the subject can be adequately dis- 



154 OUTLINES OF ORGANIC CHEMISTRY 

cussed, it will be necessary to consider the number and 
character of the isomers which are possible among the 
compounds containing two asymmetric carbon atoms. In 
such a case it is customary to assume that the rotating 
power which the compound exercises upon the plane of 
polarized light represents the algebraic sum of the rotary 
powers belonging to each asymmetric atom separately. 
This is usually spoken of as the principle of optical super- 
position, and with its aid it is easy to derive the number 
and character of the isomers corresponding to a given con- 
stitutional formula. 

The most general formula for a substance .containing two 
asymmetric carbon atoms is 



b c 



C 






I 

c 
/ l\ 

d e f 

In this formula it will be convenient to designate the rotation 
produced by that carbon atom attached to a, b, and c by X, 
and that of the other carbon atom by Y. It is then clear 
that one of the possible isomers will be one in which both 
carbon atoms tend to rotate the plane of polarized light to 
the right. Let this be called + X, +Y. Another com- 
pound will be possible in which both atoms cause rotation 
to the left. This may be called — X, — Y. The rotary 
powers of these two compounds will be equal and opposite 
and, like the two lactic acids, they will resemble each other 
closely in physical and chemical properties, and when mixed 
they will unite to form an inactive racemic compound. 

Beside the above, there must be two compounds in which 
the rotary powers of the two asymmetric atoms are exerted 



HYDROXY-ACIDS 155 

in opposite directions. These may be designated by the 
symbols +X, — Y and — X,+Y, and, like the other pair, 
they will show the usual similarities, and be capable of unit- 
ing to form another inactive racemic substance. In this con- 
nection, it is particularly important to bear in mind that 
such compounds as +X, +Y and +X, — Y are not optical 
opposites, do not as a rule unite to form bimolecular racemic 
compounds, and do show very material differences in such 
properties as melting point, crystalline form, solubility, and 
the like. Upon this fact depends one of the most important 
methods employed for splitting racemic compounds. 

We have seen in the foregoing that the maximum number of 
isomers for compounds containing two asymmetric carbon 
atoms is two pairs of optically active compounds and the 
two racemic inactive products formed by the union of these 
p airs . In__an__jjialogous- Jiiannj3r_j!_iaay: 3^,_demonst rated 
that for a substance containing n asymmetric carbon atoms 
the maximum number of optically active isomers is 2 n , 
that is, eight for three such carbon atoms, sixteen for 
four, etc. 

The number of isomers is reduced when the constitutional 
formula is symmetrical. In substances containing two asym- 
metric carbon atoms, this is the case when both of the latter 
are united to the same elements or groups. The most 
general formula for such a compound is 

a b c 

\ i / 

C 

I • 

c 

/ IN 

a b c 

This differs from the one previously given in that X= Y. 
It follows that as before there must exist two optically 



156 



OUTLINES OF ORGANIC CHEMISTRY 



active compounds, +2X and — 2X, and that these will 
form an inactive racemic compound. When, however, the 
two atoms exert their rotary power in opposite directions, 
it is clear that the result must be zero, and we shall have 
another kind of optically inactive substance which is said 
to be " inactive by internal compensation." Substances 
of this type may be distinguished experimentally from race- 
mic compounds by the fact that they cannot, like the latter, 
be split into optically active components. 



THE TARTARIC ACIDS. 



The relations just described are admirably illustrated by 
a group of well-known substances, — the tartaric acids. 
These all have the general constitutional formula indicated 
by the following syntheses of the inactive acids. 









y OH 




OH 


OH 








/ 




/ 


/ 






CN 


C=0 




c=o 


c=o 


CH 2 


/ Br 

cl 


1 
CH 2 


1 
CH 2 




1 /H 


1 /H 

c( 


II 


Br 1 ^H 3 KCN 


1 H 2 




Br 


1 X Br 


A g2 o 1 N 0H 


* k H * ' 


CH 2 


CH 2 




1 /H 


~* /H 
1 x OH 


Ethyl- 


X Br 


i 


1 




I N Br 


ene 


Ethylene 


CN 


c=o 




c=o 


C=-0 




bromide 


Succino- 
nitrile 


\ 

OH 

Succinic 




X 0H 

Di-brom 
succinic 


N 0H 

i-Tartaric 
acid 








acid 




acid 




JAg 2 










J 




OH 




H 






CN 




/ 




/ 






1 /H 




CH 2 

I 


O 


c=o 




HCN 


| \OH 

l/OH 




CH 2 




c=o 








\ 




\ 






1 X H 




OH 




H 






CN 




Glycol 




Glyoxal 






Glyoxal 



cyanhy- 
drine 



HYDROXY-ACIDS 



157 



There exist, in full confirmation of the theory, a dextro- 
rotatory and a laevorotatory acid and also two inactive ones. 
Of these, one can and the other cannot be split into the 
active components. The first of these inactive acids is 
called racemic acid (racemus, sl bunch of grapes) and the 
second meso-tartaric acid. The dextrorotatory compound is 
the ordinary tartaric acid of commerce, while Z-tartaric acid 
is a laboratory product. The configurations generally adopted 
for the different acids are represented below, both as the 
models would appear and also in the abbreviated or " pro- 
jected " form. 



H 




COOH cooh 



COOH 



OH 





OH 




OH * COOH 

d-Tartaric Acid 

COOH 
H-C-OH 
HO-C-H 
COOH 




OH 

f 



OH 



COOH OH 

I -Tartaric Acid 

COOH 
HO-C-H 




V 



H-C-OH 
COOH 



J 



H COOH 

Meso Tartaric Acid 

COOH 

, H-C-OH 

H-C-OH 

COOH 



^v 

Bacemic Acid 

Fig. 13. 

The splitting of racemic acid into its optically active com- 
ponents was historically the first operation of the kind ever 
carried out. It may be accomplished in three ways, each 
of which represents a general method applicable to cases 
of the same kind. 



158 



OUTLINES OF ORGANIC CHEMISTRY 



If a solution of the double sodium ammonium salt of 
racemic acid be allowed to evaporate at a temperature below 
28°, the salts of right and left tartaric acids separate from 
the solution in distinct crystals. If these are sufficiently 
large and well developed they can be separated mechanically, 
for while both crystallize in the same system, the crystals 
differ from each other in the same way as the models de- 
scribed on page 151 : they are enantiomorphous. The crys- 
tals of the dextrorotatory salt show upon one side certain 
unsymmetrical hemihedral faces which occur in the crystals 
of the laevorotatory salt upon the opposite side. The forms 
usually exhibited by these crystals are shown in the figure. 





/ 




7 
4 



pT 










\ 




-*m& 




U 




\ 







Fig. 14. 

The method just described is not very frequently employed 
in practice, especially where large quantities are involved, 
on account of the various mechanical difficulties which it 
presents. It is, however, extremely important because, by 
its aid, optically active compounds may be prepared with- 
out the agency of any living organism. 

A second method depends upon the action of micro- 
organisms. It is a remarkable fact that although optical 
opposites are so much alike in most of their properties, 
bacteria and similar organisms distinguish sharply between 
them. Thus if pencilium glaucum is introduced into a solu- 
tion containing racemic acid, it grows at the expense of the 
dextrorotatory compound and finally the solution rotates to 
the left. It will be observed that this method always sacri- 
fices one of the active forms. 



HYDROXY-ACIDS 159 

A third method consists in the formation of the cincho- 
nine salts. This alkaloid is itself dextrorotatory. Its addi- 
tion to a solution of racemic acid must therefore result in 
the formation of two salts which contain at least One more 
asymmetric carbon atom than the original acids. Apply- 
ing the principle of optical superposition already referred 
to on page 154, and representing the optical activity of 
cinchonine by + C, the two resulting salts may be distin- 
guished by the formulae, +X, +X, +C and —X, —X, +C. 
This means that the salts are not optical opposites. They 
may therefore be expected to differ in solubility and other 
properties, and can be separated by fractional crystallization. 
From the salts, the acids may then be set free by the action 
of a stronger acid. This last method of splitting racemic 
compounds is of the widest application. Acids, as in the 
case just cited, may be separated by combining them with 
optically active bases, or with optically active alcohols form- 
ing esters, while for the separation of racemic bases, an opti- 
cally active acid like lactic or one of the tartaric acids may 
be employed. 

d-Tartaric acid is an important natural product. It occurs 
in the juices of many fruits, and is technically obtained 
from argol, a material which deposits when wine is fer- 
mented. This can be purified by crystallization, and the 
product is then commercially known as " cream of tartar." 
It is the acid potassium salt of tartaric acid. It is exten- 
sively used in the manufacture of baking powders. The 
latter also contain sodium acid carbonate. While both 
substances are dry no reaction takes place between them, 
but when mixed with moist dough they react in the sense 
of the following equation : 

KHC 4 H 4 6 + NaHC0 3 = KNaC 4 H 4 6 + H0 2 + C0 2 . 

The carbon dioxide evolved serves to " raise " the dough. 
The neutral compound formed in the reaction is technically 



160 OUTLINES OF ORGANIC CHEMISTRY 

known as " Rochelle salt." Another well-known salt of this 
acid is " tartar-emetic." It finds some use in medicine, 
and has the following formula: C 4 H 4 6 KSbO,^H 2 0. Free 
tartaric acid crystallizes in large plates. It is readily soluble 
in water and finds extensive use in dyeing. Analytically it 
is usually recognized either by the difficult solubility of the 
acid potassium salt or by the characteristic fact that its 
calcium salt dissolves in cold dilute sodium hydroxide, but 
is again precipitated on boiling. 




<JL^«( 



''' .". mJ 
















CHAPTER IX. 

THE CARBOHYDRATES. 

There is no class of substances wherein the principles 
of stereoisomerism have proved more signally useful than 
in the case of the carbohydrates. This group includes the 
sugars, starches, gums, and cellulose. In most of these 
substances, hydrogen and oxygen are present in the same 
proportion as in water. Further, when they are treated 
with strong dehydrating agents like concentrated sulphuric 
acid, extensive decomposition takes place, accompanied by 
separation of carbon. In the earlier days of the science, 
these facts caused the whole group to be regarded as com- 
pounds of carbon and water, and this - is the historic origin 
of the name. The name is retained because the substances 
to which the term had been applied form a natural group 
with characteristic peculiarities of structure and behavior. 
Chemically this group may be said to comprise the simple 
sugars (mo noses) and substances which may be regarded 
as anhydride-like condensation products of the monoses. 
According to the number of such molecules which have 
entered into combination, the latter are classified as bioses, 
trioses, or polyoses. 

THE MONOSES. 

The simple sugars may be further defined as substances 
which combine the chemical properties of alcohols with 
those of an aldehyde or ketone. There is usually but one 
carbonyl group in a monose, but almost always there are 
several hydroxyl groups. Those sugars which are at the 

161 



162 OUTLINES OF ORGANIC CHEMISTRY 

same time alcohol and aldehyde are called aldoses; those 
which combine the character of alcohol and ketone are 
known as ketoses. The simplest possible aldose would 
therefore be 

CH 2 OH 

I 

C = 0, 

X H 

while the constitution of a simple ketose is represented by 

CH 2 OH 

1 1^<^A <U 




c=o 

I 

CH 9 OH 



A tfaf*^ 



It is usually true of the monoses that the carbon chain is 
normal, and that the number of carbon atoms is equal to the 
number of oxygens. According to the number of the latter 
which are present, the monoses are classified as tetroses, 
pentoses, hexoses, etc. 

In thinking of the physical properties of the monoses, 
the student will not go far astray if he associates them with 
those of ordinary cane sugar, which, however, does not 
belong to this class. They are crystalline solids, usually 
very soluble in water and but slightly soluble in most organic 
solvents. They have a more or less sweet taste, and when 
heated above their melting points or treated with dehy- 
drating agents they readily char. 

The monoses which are most commonly met with, and 
the only ones which will receive individual consideration 
here are the hexoses. As suggested above, these fall natu- 
rally into two classes, the aldohexoses and the ketohexoses. 
The constitution assigned to these two classes of compounds 
is shown in the following formula?: 



THE CARBOHYDRATES 163 

CH 2 OH CH 2 OH 

I I 

*CHOH *CHOH 

I I 

Aldohexose *CHOH *CHOH Ketohexose 

I I 

*CHOH *CHOH 

I I 

*CHOH C = 

I I 

C • HO CH 2 OH 

The experimental evidence upon which these formulae are 
based rests, among other things, upon the following facts. 
Reduction leads to the formation of hexatomic alcohols, 
which "in "turn yield secondary hexyl iodide, 

CH 3 ■ CH 2 • CH 2 • CH 2 • CHI ■ CH 3 . 

This proves the presence of a normal carbon chain. Acetic 
anhydride forms pent acetates, showing the presence of five 
hydro xyl groups. The distribution of the latter is deter- 
mined by the well-known empirical rule that two or more 
hydroxyl groups usually cannot remain attached to the 
same carbon atom. Finally the distinction between the 
aldoses and ketoses rests upon the difference of behavior 
upon oxidation. The former yield acids containing the same 
number of carbon atoms. The ketoses, however, yield 
products containing less than six carbon atoms. The loca- 
tion of the carbonyl group follows from the constitution 
of the oxidation products. These' fundamental proofs are 
supplemented by a large number of genetic relationships 
which exist between the different isomers, and which are in 
harmony with the constitution outlined. This leads to a 
discussion of the possibilities of stereoisomerism involved. 
An examination of the formulge just given reveals the fact 
that the aldokex oses contain four asymme tric carbon atoms, 
while the ketohexoses contain three. According to the rule 



9^^ 



64 OUTLINES OF ORGANIC CHEMISTRY 

that the number of optical isomers is 2 n , where n is the num- 
ber of asymmetric carbon atoms, it follows that for an 
aldohexose of the formula given eight pairs of optical oppo- 
sites are possible, in addition to eight racemic compounds 
formed by the mixture of these two. Of the ketoses there 
will be considerably less, viz. : four optically active pairs and 
four racemic compounds. Most of these isomers are actually 
known, and the configurations of each have been determined 
with considerable certainty. The methods of proof which 
are employed in each case need not be entered into here. 
It is sufficient to say that they rest upon the same kind of 
reasoning as that employed in determining the configura- 
tions of the tartaric acids. Some of these compounds are 
extremely important both in nature and technically. 

d-Glucose, also known as grape sugar and as dextrose, is 
found in the juices of most sweet fruits. It is a colorless, 
crystalline solid of a sweetish taste, which, however, is 
much less marked than that of cane sugar. Crystals con- 
taining water appear in several modifications. From methyl 
alcohol, d-glucose crystallizes without water, and then melts 
at 146°. It rotates the plane of polarized light to the right, 
and reduces alkaline silver and copper solutions (Fehling's 
solution). Either of these properties can be utilized for its 
quantitative determination. Its accepted configuration is 

CH 2 OH 




THE CARBOHYDRATES 165 

It is extremely widely distributed in nature, occurring free 
in the juices of many fruits, but more often combined with 
other sugars in the form of bi-, tri-, or polyoses, as well as 
with other classes of compounds in the substances known 
as glucosides. These various classes will be mentioned again 
later on. d-Glucose also plays a very important role in 
animal nutrition, and in certain pathological conditions {dia- 
betes mellitus) it is a constituent of the urine. 

Commercial glucose is a product obtained on the large 
scale by the hydrolysis of starch. It is not pure d-glucose, 
though it contains a large percentage of this substance. It 
finds extensive use as a sweetening material in the manu- 
facture of preserves and confectionery. It has also been 
employed as an adulterant of honey. Both the product and 
the process of formation will again be touched upon when 
we take up the study of starch. 

d-Galactose is another aldohexose. It is obtained by 
the hydrolysis of milk sugar. It crystallizes in fine needles 
which melt at 166°. Its configurationTls"" 

CH 2 OH 
I 
HO-C-H 
I 
H-C-OH 

I 
H-C-OH 
I 
HO-C-H 
I 
CHO . 

Of the ketohexoses only one need be mentioned, d-fruc- 
tose. This substance is also known as fruit sugar and levu- 
lose. It occurs in fruit juices and in honey along with 
c^glucose. It forms hard rhombic crystals which melt at 95°. 
Its solutions rotate" the 'plane of polarized light to the left. 



166 OUTLINES OF ORGANIC CHEMISTRY 

This last fact suggests the query : — why should the sub- 
stance be called d-fructose if it rotates to the left? As 
was pointed out on page 152 the letters d- and 1-, when pre- 
fixed to the names of the carbohydrates or related sub- 
stances, do not indicate the direction of rotation of the spe- 
cific compound, but rather whether it is genetically related 
to d- or Z-glucose. In the present case, the relation to 
rf-glucose is traced in the following manner. There is an aro- 
matic compound called phenyl hydrazine whose formula is 

H ' N - N XC 6 H 5 - 

This substance reacts with d-glucose to form a compound 
called d-gjucosazons which has the constitution indicated 
by the following formula: 

CH 2 OH 

I 
HO-C-H 

I 
HO-C-H 

I 
H-C-OH 

I 

C = N-NH-C 6 H 5 

* I 

H-C = N-NH-C 6 H 5 . 

Exactly the same compound is produced when phenyl hy- 
drazine reacts with fruit sugar. Now it will be noted that 
the formula of the glucosazone contains but three asym- 
metric carbon atoms, and since this compound is formed 
from both grape and fruit sugars, it follows that three^of 
the asymmetric carbon atoms of d-glucose have the same 
arrangement in the molecule as the three of fruit sugar. 
From this it follows that the constitution of the latter must 
be correctly represented by the following formula; 







•/ 



THE CARBOHYDRATES 167 

CH 2 OH CH 2 OH 

I I 

HO-C-H HO-C-H 

I I 

HO-C-H HO-C-H 

I d-glucose being I 

H-C-OH H-C-OH 

I I 

C=0 HO-C-H 

I I 

CH 2 OH C-0 . 

\ 
H 

Consequently it is properly named d-fructose. It should 
be added that Z-glucose and Z-fructose are also well known, 
but have no practical importance. They show scarcely any 
difference from the corresponding d-compounds except in 
their action- upon the plane of polarized light. 

FERMENTATION. 

Since the earliest times it has been known that when 
dilute sugar solutions are left standing exposed to the air, 
gas is evolved and alcohol accumulates in the solution. 
The production of alcoholic beverages rested upon this fact. 
An early improvement in the process consisted in bringing 
into the solution some material like yeast, instead of trust- 
ing to the chance inoculation of the air. In later times it 
was found that if grape sugar were the material fermented, 
the reaction was nearly quantitative in the sense of the 
following equation : 

C 6 H 12 6 =2C 2 H 5 OH + 2C0 2 . 

The nature of the processes involved in fermentation has 
been differently interpreted at different times. It was the 
idea of Liebig that the atoms of a substance like sugar were 
in a constant state of vibration which was, however, under 



168 OUTLINES OF ORGANIC CHEMISTRY 

ordinary circumstances, restricted within certain limits. In 
the presence of micro-organisms, however, ^his vibratory 
motion was so far stimulated that it exceeded the bounds 
of chemical affinity and the compound broke up. This view 
was contested by Pasteur, who was able to show, in the first 
place, that when micro-organisms were carefully excluded, 
no fermentation took place; and further, that different fer- 
mentations were induced by different micro-organisms. 
Thus while grape sugar with yeast yields alcohol, with an- 
other organism (bacillus acidi lactici) it yields lactic acid. 
These facts caused fermentation to be looked upon as in 
some obscure way related to the vital processes of the micro- 
organisms employed, and until recently this has been the 
dominant view, in spite of the fact that, in course of time, 
products had been discovered which contained no living 
cells, and yet by their presence caused or rather catalyzed 
certain chemical reactions. It thus became necessary to 
draw a distinction between materials like yeast which were 
called " formed ferments," and these other substances, 
which were now called " unformed ferments " or enzymes. 
Of the nature of the latter or of their chemical action we 
really have no knowledge. As a matter of fact, no pure 
enzyme has probably ever been isolated, and we know the 
active principle only by its action. An illustration may be 
found in the case of the gastric juice. It is known that in 
the stomach our food " digests." This action, as we shall 
see later, is essentially a hydrolysis which is accelerated by 
the action of the secretions of the walls of the stomach. 
From these juices there can be isolated a white amorphous 
powder which appears to belong to the class of substances 
known as proteins. This powder, when added to materials 
like the foods, outside the stomach, induces hydrolytic action. 
We say, therefore, that the powder contains the active enzyme 
" pepsin " which causes gastric digestion. It is to be noted 



THE CARBOHYDRATES 169 

that we should say the powder contains rather than is pepsin, 
for, in the first place, the properties of substances of this kind 
offer no guaranty of purity or homogeneity, and, secondly, 
different samples of otherwise similar appearance show dif- 
ferent efficiency. From these facts, we are assured that we 
do not know the enzymes as such, but only their effects. 

The distinction between formed and unformed ferments 
has now lost practically all significance, since the recent 
discovery that it is possible to induce alcoholic fermentation 
in a sugar solution by adding to it the extract from crushed 
yeast cells. Biological tests have shown that this material 
contains no living cells, and yet it causes the same fermenta- 
tion as the living yeast. The conclusion seems unavoidable 
that the fermentation produced by the yeast itself has little 
to do with its vital processes, but rather is due to an enzyme 
which it contains. This particular ferment has received 
the name " zymase." It is probably true that the fermenta- 
tions produced by other micro-organisms are due to similar 
causes. How the enzyme produces the fermentation is, of 
course, as little understood as ever. It simply holds true 
that this catalysis takes place. 

A word may not be out of place here upon the subject of 
catalysis in general. A catalyzer is now defined as a sub- 
stance whose presence increases the velocity of a chemical 
reaction without itself being used up by the reaction. Cata- 
lyzers have therefore been appropriately compared to the 
oil which lubricates machinery, thus causing it to go faster 
without itself contributing any energy. A single simple 
chemical illustration will suffice. Hydrogen peroxide is a 
somewhat unstable compound which, even in quite dilute 
aqueous solution, decomposes slowly into oxygen and water. 
If there be introduced into such a solution a little powdered 
manganese dioxide, the evolution of oxygen becomes brisk, 
and decomposition is complete in a short time* The same 



170 OUTLINES OF ORGANIC CHEMISTRY 

effect will be produced if there be brought into the solution 
a little blood. The blood contains a ferment whose presence 
accelerates the decomposition of the hydrogen peroxide. 
How it is that these two so different substances should 
produce so similar an effect is entirely unknown to us. In 
some reactions of this type, it has been shown that the cata- 
lyzer first enters into combination with one of the reacting 
substances, and then in a second reaction is again regen- 
erated. Whether this holds true in either of the present 
instances we do not know, nor do we know whether there 
is any real analogy between the mechanisms of the two 
reactions. We only know that the same end products are 
formed in each case, and we call both actions catalytic. 

In the case of the enzymes or organic catalyzers, one fact 
must be especially emphasized. Their action is in high de- 
gree specific. This applies both to the material acted upon 
and to the reaction induced. Thus yeast ferments d-fructose 
with ease, while it acts but slowly upon Z-fructose. So, too, 
yeast causes d-glucose to decompose into alcohol and carbon 
dioxide, while other enzymes may produce lactic or butyric 
acid, or other products. Emil Fischer has well compared the 
relation which exists between enzyme and fermenting sub- 
stance to that between lock and key. Probably there is no 
more striking example of this than the fact that the enzymes 
act so differently upon optical opposites, substances which 
are so exactly alike in most other particulars. 

THE BIOSES^ 

This name has been given to a class of substances which 
may be considered as derived from two like or unlike mole- 
cules of monoses by the elimination of one molecule of water. 
Their physical properties are in general quite similar to 
those of the monoses. When the bioses are treated with 
hydrolyzing agents, the monoses are again regenerated. For 



THE CARBOHYDRATES 171 

carrying out such h ydrcrtyseSj. the bioses may either be 
t reated with water under pressure, or boiled with dilute 
acids (alkalies act more slowly) or finally subjected to the 
action of certain enzymes. The more important bioses have 
the general formula C 12 H 22 O u and when hydrolyzed yield 
monoses in accordance with the equation, 

C 12 H 22 O u + H 2 = 2C 6 H 12 6 . 

There are a great many bioses, as might be expected when 
it is recalled how many hydroxyl groups the monoses con- 
tain, and consequently in how many different ways water 
might be eliminated. This also makes it difficult to deter- 
mine the constitution of the bioses. A few important ones 
will receive individual consideration. 

Sucrose, or cane sugar, is a most important article of food. 
It occurs in the juices of many plants, notably of the sugar 
cane, the beet, the sugar maple, sorghum, etc. It is a color- 
less solid which may be crystallized from water, in which it 
is extremely soluble. It melts at 160°, and its solutions 
rotate the plane of polarized light to the right. This 
property is the one usually made use of in the quantitative 
determination of sugar. Since the angle of rotation is 
directly proportional to the concentration of the solution, 
the former serves as a direct measure of the latter when no 
other optically active substance is present. When cane 
sugar is heated above its melting point, a brown ill-charac- 
terized product called caramel is formed. This is extensively 
used to impart a dark color to certain food products or 
beverages. When the caramel is further heated, extensive 
decomposition takes place, accompanied by carbonization. 
Cane sugar, .does not reduce ammo niaoal silver solutions or 
Fehling's solution. It is therefore not an aldehyde, and it 
may be inferred that in its formation the aldehyde oxygen 
of the d-glucose was the oxygen atom lost in the condensa- 



172 OUTLINES OF ORGANIC CHEMISTRY 

tion. Several constitutional formula? have been proposed 
for cane sugar, but none of them can as yet be regarded as 
definitely established. By hydrolytic agents cane sugar is 
smoothly decomposed. The products are one molecule of 
d-glucose and one molecule of d-fructose for each molecule 
of sucrose hydrolyzed. Since ^fructose rotates the plane 
of polarized light to the left more strongly (for equivalent 
concentrations) than d-glucose rotates it to the right, such 
a molecular mixture of the two monoses is laevorotatory. 
As cane sugar itself is dextrorotatory, it follows that when 
its solutions are hydrolyzed, a reversal of the direction of 
rotation is observed. On this account the hydrolysis of 
cane sugar has received the specific name, inversion and 
the molecular mixture of d-glucose and c?-fructose which con- 
stitutes the product is called inju&xLij^ar . Cane sugar is not 
directly fermented by zymase. When it is treated with yeast, 
fermentation cannot take place until hydrolysis has been 
effected by another enzyme also present which is called 
invertase on account of this action. It is an interesting fact 
that invert sugar is occasionally met with in nature. Honey 
is one of the most marked examples. 

Lactose or milk sugar, as its name indicates, is the sub- 
stance to which milk is indebted for its sweet taste. In order 
to prepare it from skimmed milk, the casein of the latter is 
first coagulated and precipitated by acids; then the albu- 
mins are removed by boiling, and finally the solution is evap- 
orated. Milk sugar is by no means as sweet as cane sugar. 
It is a reducing agent, and hence in contradistinction to cane 
sugar it probably contains an aldehyde group. Upon hydrol- 
ysis it yields one molecule of d-glucose and one of d-galactose. 
This accounts for the name of the latter compound. 

Maltose or malt sugar is a most important intermediate 
product in the technical production of alcohol. It is best 
prepared by the hydrolysis of starch under the influence of 



THE CARBOHYDRATES 175 

opalescent semi-solution with water. Starch may be h y- 
drolyzed either by ferments or by dilute acids. The first 
products formed are of high molecular weight and closely 
allied to starch. They bear a variety of names, — " soluble 
starch/' " amy lo dextrin," " dextrin," etc. These names, how- 
ever, can hardly be held to stand for distinct chemical in- 
dividuals, but rather for complexes of starch molecules in 
various degrees of disintegration. The first well-defined prod- 
uct of hydrolysis is maltose. This is produced under the in- 
fluence of diastase, and we know that upon further hydroly- 
sis, it yields d-glucose. It follows that the starch molecule, 
however complicated its constitution, is essentially an 
anhydride-like union of molecules of d-glucose. 

The hydrolysis of starch is carried out industrially with 
two objects in view. The first is the preparation of ethyl 
alcohol from grain. After the grain has been well soaked, 
malt is added in order that the diastase which it contains 
may hydrolyze the starch of the grain, forming maltose. 
Yeast is then allowed to act upon the maltose, forming 
alcohol. 

The second, which consists in the hydrolysis of starch by 
acids, yields commercial glucose and dextrin. The latter 
is the chief impurity in commercial glucose. The properties 
and uses of glucose have already been mentioned. Dex- 
trin, which is a gummy, amorphous material, finds extensive 
employment as a cheap and efficient adhesive, suitable for 
use upon the flaps of envelopes, the backs of postage stamps, 
and the like. 

The Gums. These are natural products usually occurring 
as exudations from trees. Their composition is not very 
uniform nor their properties well characterized. In general, 
most of them are to be considered as polyoses or dextrin- 
like derivatives of the latter. Many of them upon hydroly- 
sis yield pentoses. 



176 OUTLINES OF ORGANIC CHEMISTRY 



XL** 



CELLULOSE. 



In cellulose the resemblance to the sugars in physical 
properties has disappeared. The sweet taste and solubility 
in water which are characteristic of most of the carbohydrates 
are here entirely lacking, and the substance is very inert 
toward almost all reagents. These properties fit it admirably 
for its important place in nature. It forms an essential 
part of the cell walls of plants and is an important component 
of woody fiber. Hence it is probably the most widely dis- 
tributed substance in the vegetable world. The most con- 
venient source for the production of pure cellulose is the 
cotton fiber, and " absorbent cotton " (cotton from which 
the fatty materials have been removed by extraction) is 
nearly pure cellulose. The so-called " Swedish " filter paper 
— paper from which the mineral contents have been re- 
moved by treatment with hydrochloric and hydrofluoric 
acids — is perhaps a still purer form. 

The propriety of classifying cellulose with the carbohy- 
drates is seen in its behavior upon hydrolysis. If filter paper 
is covered with cold concentrated sulphuric acid, it soon 
goes into solution without charring. If this solution be now 
diluted and boiled, it is found to contain d-glucose. One of 
the intermediate products of hydrolysis is a biose called eel- 
lose. This is supposed to stand in the same relation to cellu- 
lose which maltose does to starch. like the latter, cellulose 
must be a polymerized condensation product of d-gl ucose > 
but whether its molecular weight is greater or less than that 
of starch is only a matter of conjecture. 

If cellulose be treated with a less concentrated sulphuric 
acid for a short time it becomes partly gelatinized, and the 
product when washed out and dried is a tough hard material 
resembling parchment. The material has received the name 
of " amyloid " (Latin, amylum, starch) on account of the 



THE CARBOHYDRATES 177 

blue color which it gives with iodine. It is, no doubt, a 
partially hydrolyzed cellulose. 

Potassium and sodium hydroxides in moderately concen- 
trated solutions also have a peculiar effect upon cotton fiber. 
They cause a twisting and shrinking which strengthen the 
fiber, and if the latter be thus treated while under tension, 
it acquires luster. This gives to the product a certain 
resemblance to silk, and cotton goods treated in this way 
have enjoyed considerable popularity. The process is known 
as " mercerization," from the name of its inventor. 

Certain rather unusual reagents dissolve cellulose quite 
readily with little apparent chemical change. One such 
medium is a mixture of zinc chloride and hydrochloric acid. 
Another is a solution of cupric hydroxide in ammonia. 
This reagent is best prepared by allowing metallic copper 
to stand in aqueous ammonia while a current of air or oxygen 
is passed through the liquid. When cellulose is covered 
with the solvent it first gelatinizes, and then becomes grad- 
ually distributed throughout the liquid. The solution is 
typically colloidal. From it the cellulose may be precipi- 
tated again as an amorphous powder, either by treatment 
with acids or by dilution with water or alcohol. In any case, 
the product contains a little water which is perhaps chemi- 
cally combined. 

By the action of acids and acid anhydrides upon cellulose, 
esters are formed: some of these are of great technical 
importance. From the extent to which esterification takes 
place, the conclusion is justified that cellulose contains six 
hydroxyl groups for each twelve atoms of carbon. Its 
empirical formula [C 12 H 20 O 10 ]a; may therefore be expanded 
to [C 12 H 14 4 (OH) 6 ]. x 

Cellulose Nitrates. If cellulose be treated with a mix- 
ture of highly concentrated nitric and sulphuric acids, six 
nitric acid radicles are introduced into the molecule, and the 



178 OUTLINES OP ORGANIC CHEMISTRY 

product may be given the formula [C 12 H 14 4 (N0 3 ) 6 ] a; . This 
hexanitrate closely resembles cellulose itself in physical 
properties. If it be prepared from cotton, the fibers are, 
perhaps, a little more harsh to the touch, but otherwise little 
is noticed which would distinguish it from the original cotton. 
When dry, nitroce llulose is readily combustible, and when 
ignited by means of mercury fulminate, it explodes with 
great violence. It is commonly known as gun-cotton or 
pyroxylene. As an explosive it has several advantages. 
One of the chief of these is that when wet it is practically 
non-combustible, yet the wet gun-cotton will explode like 
the dry, if it be first ignited by the explosion of some of the 
dry material. This makes it practicable to store, trans- 
port, and use the explosive in the wet condition, only keep- 
ing enough of the dry on hand to serve as priming. 

If the acids used in the nitrating mixture are more dilute 
than above described, esters are obtained which contain 
fewer nitric acid groups, usually four or five. In appearance 
there is not much to distinguish these various nitrates, but 
the lower ones are, as a rule, more soluble in organic liquids, 
particularly in a mixture of alcohol and ether. It should 
be distinctly understood in this connection that solubility 
in organic solvents is not to be regarded as an infallible clue 
to the degree of nitration of a nitrocellulose. Tetranitrates 
have sometimes proved as insoluble in these media as the 
hexanitrate itself. The properties of the nitrate seem in 
general to depend fully as much upon the conditions of 
nitration as upon ths percentage composition of the product. 
It is doubtful whether these lower nitrates of cellulose should 
in any case be considered as distinct chemical individuals. 
A solution of cellulose nitrate in alcohol and ether is com- 
monly known as collodion. On evaporation of the solvent, 
the cellulose nitrates are deposited as a coherent, elastic, 
transparent film. This makes collodion a convenient thing 



THE CARBOHYDRATES 179 

to paint upon scratches or abrasions of the skin in order 
to protect them from the irritating action of the air. Col- 
lodion is also frequently used as a varnish where a perfectly 
colorless coating is desired, as for example for photographic 
negatives. Here any color would retard printing. 

When lower nitrates of cellulose or " collodion cotton" 
are mixed with camphor, either in solution or mechanically, 
a product is formed which is not explosive and whose proper- 
ties fit it for a great number of applications. This is cellu- 
loid, whose use in films and as a cheap- substitute for bone 
"and ivory is so well known. It is unfortunately very com- 
bustible, and this is a serious objection to its use especially 
in the manufacture of objects of large size. 

Smokeless Powder. When gun-cotton or a slightly lower 
nitrate of cellulose is treated with certain organic solvents — 
usually mixtures containing a good deal of acetone — it 
gelatinizes, forming a non-fibrous mass which can be pressed 
into any shape. After evaporation of the acetone there is 
left a hard yellow substance somewhat like tortoise shell. 
This is the material from which " smokeless powder " is made. 
It is brought upon the market in grains and cylinders of 
various forms and sizes. It is faster burning than black 
powder, cleaner in the gun, and for military purposes has 
the advantage of not obscuring the view by clouds of smoke. 
When nitro-glycerin is absorbed by cellulose nitrates, a 
material called "blasting gelatin" is produced. 

Cellulose Acetates. When cellulose is treated with 
acetic anhydride in the presence of small amounts of sul- 
phuric acid or of zinc chloride, six hydro xyls are esterified. 
The product is generally known technically as the "tri- 
acetate." This term involves an inconsistency in nomen- 
clature which requires a word of explanation. Since the 
molecular weight of cellulose is unknown, there is no objection 
so far as cellulose itself is concerned to writing its formula 



180 OUTLINES OF ORGANIC CHEMISTRY 

[C 6 H 7 2 (OH) 3 ]z instead of C 12 H 14 4 (OH) 6 ]„ tacitly giving 
to x in the first case twice the value it has in the second. 
Nitrates of cellulose, however, appear to exist which con- 
tain three and five nitric acid groups respectively for each 
twelve atoms of carbon in cellulose. For them no formula 
can be written upon a six-carbon-atom basis which does not 
involve the use of fractional molecules or groups. Conse- 
quently the twelve-carbon formula for cellulose is practi- 
cally always used when speaking of the nitrates. With the 
acetates the case is -somewhat different. Of these, three are 
known, the one just mentioned, and two others containing 
respectively one-third and two-thirds as many acetyl groups. 
When acetates alone are considered, therefore, it involves no 
inconsistency to call these products mono-, di-, and triace- 
tates of cellulose, and to assign to the most highly acylated 
product the formula [C 6 H 7 2 (C 2 H 3 2 ) 3 ]x. To put this into a 
form which should bring out its relation to the correspond- 
ing nitrate, it should be written [C 12 H 14 4 (C 2 H 3 2 ) 6 ]x and 
called a hexacetate. Unfortunately this has not been done in 
practice, and consequently the student must bear in mind 
that the product commonly called cellulose " triacetate " 
represents a degree of esterification of the cellulose mole- 
cule corresponding to that designated by the term "hexa- 
nitrate.' , 

This acetate, whatever name be given it, much resembles 
the nitrates in physical properties. It is soluble in a variety 
of organic solvents, notably in chloroform. From such 
solutions it is deposited as a tough transparent film, which 
has the practical advantage over that formed by the nitrate 
that it is not explosive, and no more combustible than the 
original cellulose in a similar state of subdivision. Cellulose 
acetate has also been used as an insulating material for fine 
copper wire like that used for winding the small electro- 
magnets of telegraph and telephone instruments. For most 



THE CARBOHYDRATES 181 

purposes its relatively high cost of production has pre- 
vented its extensive employment. 

Artificial Silk. Various attempts have been made to 
prepare from cellulose some cheap substitute for silk. The 
earliest methods involved the use of collodion. Solutions 
of cellulose nitrate were forced through fine apertures un3er 
water, and in this way there was formed a fine thread which 
could be dried, spun, and woven like any other fabric. Such 
a product has a luster rather superior to that of natural silk. 
It also can be easily dyed and so is well fitted to replace the 
latter for ornamental purposes, though where wearing quali- 
ties are required it cannot be used to advantage on account 
of its low tensile strength. The product just described has 
all the further disadvantages associated with the combusti- 
bility of the cellulose nitrate, and is no longer brought on the 
market in its original form. By passing the fibers through 
calcium sulphide solution a " denitrification " is effected. 
This is a saponification by which cellulose is regenerated. 
The action does not seem to sensibly affect the physical 
properties of the fiber. Cellulose acetate, the solution of 
cellulose in ammoniacal cupric oxide, and other cellulose 
products have also been used for the manufacture of 
artificial silk. Fine effects can be obtained by all proc- 
esses, but none has thus far produced a fiber equal in 
strength and durability to natural silk. A word on the 
distinction of artificial from natural silk may not be out of 
place. Natural silk being albuminous gives when burning 
the odor commonly associated with burned feathers. No 
cellulose product does this when pure. When observed 
under the microscope the fibers of artificial silk are round, 
while those of the natural product have a cross-section like 
the figure 8, 



CHAPTER X. 

DERIVATIVES OF CYANOGEN AND CARBONIC ACID. 

CYANOGEN AND ITS DERIVATIVES. 

Among the compounds related to cyanogen, the nitriles 
have already been touched upon (page 74), and the be- 
havior of the simpler cyanides is doubtless already familiar 
to the student from his work in Inorganic and Analytical 
Chemistry. Nevertheless a brief recapitulation will not be 
out of place at this point. 

When animal refuse containing nitrogen (hoofs and horns 
for example) is heated with potash and metallic iron, 
complicated reactions take place, and the resulting melt 
when leached out with water yields potassium ferrocya- 
nide, K 4 Fe(CN) 6 , which crystallizes in large yellow aggre- 
gates. This substance is known commercially as " yellow 
prussiate of potash." When treated with oxidizing agents 
such as chlorine water, it is changed to the ferricyanide, 
commonly known as " red prussiate of potash ": 

2 K 4 Fe(CN) 6 +C1 2 = 2 KC1 +2 K 3 Fe(CN) 6 . 

These compounds are not to be looked upon as double 
cyanides of iron and potassium but rather as potassium 
salts of the acids H 4 Fe(CN) 6 and H 3 Fe(CN) 6 . As such they 
undergo various metathetic reactions with salts of various 
metals, for example with iron. When potassium ferro- 
cyanide is treated with the solution of a ferric salt, a dark 
blue precipitate is produced: 

4 FeCl 3 +3 K 4 Fe(FN) 6 = 12 KC1 + Fe 4 [Fe(CN) 6 ] 3 . 

As the above equation indicates, this product is usually 

182 



CYANOGEN AND CARBONIC ACID 183 

regarded as a ferric ferrocyanide. It is much used as a 
pigment and is commonly called " Prussian blue." An alto- 
gether similar precipitate is formed when a soluble ferri- 
cyanide is treated with a ferrous salt. The product in this 
case is usually spoken of as " Turnbull's blue," but recent 
investigations have made it not improbable that the two 
pigments are identical. 
\ Hydrocyanic Acid. The more complicated cyanogen 
compounds have been considered first, because technically 
they are the source of the simpler ones. If potassium ferro- 
cyanide is heated to fusion, decomposition takes place which 
results in the formation of nitrogen, metallic iron, carbon, and 
potassium cyanide: 

K 4 FeCN 6 = N 2 + Fe +C 2 +4 KCN. 

The last is a colorless salt extremely soluble in water and 
very poisonous. If this salt be treated with dilute acids, 
it is decomposed with liberation of hydrocyanic acid: 

KCN + HC1 = KC1+HCN. 

This decomposition is even effected to a certain extent by 
the carbon dioxide of the air. The free acid, commonly 
called " prussic acid," is usually obtained in the laboratory 
by the distillation of potassium ferrocyanide with dilute 
sulphuric acid: 

K 4 Fe(CN) 6 + 5 H 2 S0 4 = 6 HCN + FeS0 4 + 4 KHS0 4 . 

The product is first passed through calcium chloride in 
order to remove any water and then condensed. It is a 
volatile liquid boiling at 26° and freezing at — 15°. It has 
a peculiar, characteristic odor which, however, some persons 
are unable to perceive. It is extremely poisonous. The 
anhydrous liquid is stable, but with small amounts of water 
decomposition gradually takes place, resulting in the for- 
mation of the ammonium salts of formic and oxalic acids. 



184 OUTLINES OF ORGANIC CHEMISTRY 

As its formula indicates, prussic acid may be regarded aa 
the nitrile of the former: 

HCN +2 H 2 = NH 3 +HCOOH . 

On reduction, methyl amine is formed: 

HCN+H 2 = CH 3 -NH 2 , 

and this is in entire accord with the behavior of the organic 
nitriles. 

The salts of hydrocyanic acid show a marked tendency to 
form complex ions in aqueous solution with the salts of 
various metals. The solubility of the halogen compounds 
of silver in potassium cyanide is attributed to this cause, 
and the tendency is further illustrated by the existence of 
the complex iron compounds already described. The ferro- 
cyanides are readily formed when a ferrous salt is digested 
in alkaline solution with a soluble cyanide : 

FeS0 4 +6KCN = K 4 Fe(CN) 6 + K 2 S0 4 . 

Cyanogen. When mercuric cyanide is heated, it de- 
composes into metallic mercury and cyanogen, or as it is 
frequently called, dicyanogen: 

CN 
HgCN 2 = Hg + l . 
CN 

The same substance is formed when the sparks of an induc- 
tion coil pass between carbon electrodes in an atmosphere 
of nitrogen: 

CN 
C 2 +N 2 = I . 
CN 

Cyanogen is a gas with an odor suggestive of bitter almonds, 
and like hydrocyanic acid, it is extremely poisonous. It 
can be condensed to a liquid at — 25°, and burns with a 
characteristic purple-bordered flame. It may be regarded 



CYANOGEN AND CARBONIC ACID 185 

as the nitrile of oxalic acid. In this connection, it is in- 
teresting to note that it may be prepared by the dehydrating 
action of phosphorus pentoxide upon ammonium oxalate: 

COONH 4 CN 

I =4H 2 0+ I . 

COONH 4 CN 

Cyanates. If a solution of potassium cyanide be oxi- 
dized by permanganate, the cyanate is formed: 
KCN+O = KCNO. 

The corresponding ammonium salt is of interest on account 
of its spontaneous transformation into urea : 

/NH 3 
NH 4 CNO = CO 

X NH 2 

Sulphocyanates. The sulphocyanates of the alkali 
metals are frequently employed in Analytical Chemistry. 
The student will doubtless recall the deep red color which 
they produce with ferric salts, 

FeCl 3 +3 KSCN = Fe(SCN) 3 + 3 KC1 , 

and their usefulness in the determination of copper and 
silver.. The sulphocyanates are easily prepared by fusing 
the cyanides with sulphur or by digesting them with a 
polysulphide : 

KCN+S = KSCN. 

NH 4 CN + (NH 4 ) a &,. = NH 4 SCN + (NH^S^ . 

The mercury salt of sulphocyanic acid swells up and 
assumes the most grotesque forms when heated. The pellets 
commonly sold as playthings under the name " Pharaoh's 
serpents " consist of this material. It is doubtful whether 
their unrestricted use is entirely safe, both on account of the 
poisonous character of mercury salts, and because of the 
gases liable to be evolved when the material is ignited. 



186 OUTLINES OF ORGANIC CHEMISTRY 



CARBONIC ACID DERIVATIVES. 

On account of the common occurrence of the carbonates 
as minerals (calcite, dolomite, etc.), carbonic acid is usually 
thought of as belonging to Inorganic Chemistry. It is allied, 
however, to a great number of organic substances and it is, 
strictly speaking, the simplest member of the series of dibasic 
organic acids. An intimate acquaintance with the chem- 
istry of the organic derivatives of carbonic acid is hardly 
necessary for any save the professional organic chemist, but 
a few of them deserve some mention here. In general, it 
may be said that the properties and methods of preparation 
of these substances do not differ widely from those of analo- 
gous compounds in other series; thus the esters are formed, 
for example, by the action of the alkyl halides upon silver 
carbonate, or by the action of the chloride of carbonic acid 
upon the alcohols, and their properties are much the same 
as those of other esters. 

Phosgen. The symmetrical chloride of carbonic acid is 
an interesting substance. It can be prepared by the action 
of chlorine upon carbon monoxide under the influence of 
light. This reaction was historically one of the first " photo- 
chemical reactions "to be observed, and from this method 
of formation the substance itself received the name phos- 
gen (Greek, <£u>s, light). A method of preparation which is 
more convenient for practical purposes consists in the action 
of fuming sulphuric acid upon carbon tetrachloride. This 
rather peculiar reaction proceeds in accordance with the 
following equation : 

/C i 

H 2 S 2 O r + CCl, = C = 0+H 2 0+S 2 5 C1,. 
X C1 
The last product is called pyrosulphuryl chloride. 



CYANOGEN AND CARBONIC ACID 187 

Phosgen is a colorless gas which, however, is easily con- 
densed by a freezing mixture. It dissolves readily in toluene 
and such a solution is usually employed for keeping and 
transporting it. It possesses the usual physical and chemi- 
cal properties of the acid chlorides including an intolerable 
odor. As might be expected, it acts upon alcohols forming 
esters, with ammonia to form amides, and, in a variety of 
other ways, proves a valuable reagent. 

Amides: Urea. Since carbonic acid is dibasic, two amides 
are possible. The first is commonly known as carbamic acid. 
Its ammonium salt is formed when carbon dioxide reacts 
directly with ammonia gas: 

/ ONH 4 
C0 2 +2NH 3 = C = 
X NH 2 

and hence is always present to some extent in commercial 
ammonium carbonate. 

A compound of far greater interest is the symmetrical 
amide named carbamide, or more commonly, urea. This 
substance is of great interest to the physiologist, since in 
mammals it is in the form of urea that practically all the 
nitrogen which originally enters the organism in the food 
is finally again eliminated from it. The amount of urea 
secreted is regarded as a measure of the albuminous material 
decomposed by the body. The average amount of this 
substance which is produced daily by an adult man may be 
roughly estimated at about thirty grams. The quantity 
varies a good deal according to the diet and the state of 
health, so that a determination of the quantity produced in 
a given time is often a valuable aid in diagnosis. 

In the laboratory, urea may be formed by the customary 
methods for preparing acid amides, such as the action of 
ammonia upon phosgen or upon the esters: 



188 OUTLINES OF ORGANIC CHEMISTRY 

/CI NH 2 

C = + 4 NH 3 = 2 NH 4 C1 + C = . 

N CI x NH 2 



/OC.H, /NH 



C = +2 NH 3 = C = +2 C 2 H 5 OH. 

N OC 2 H 5 X NH 2 

A more interesting method, as well as one which is more 
convenient in practice, depends upon the molecular rear- 
rangement by which urea is formed from ammonium cyanate: 

/NH 2 

NH 4 OCN = C = . 

X NH 2 

This takes place upon merely evaporating the aqueous 
solution of the salt. The reaction was first observed by 
Wohler in 1828 and had great historical significance. At 
the time this discovery was made, those substances were 
classed as " organic " which were produced directly or 
indirectly from the animal or vegetable organism. It was 
believed that such substances could come into existence only 
in this way, and that while inorganic compounds were held 
together by chemical affinity — then supposed to be elec- 
trical in character — the organic ones owed their formation 
and preservation to the action of the " vital force." The 
formation of urea, a typical product of the animal organism, 
from ammonium cyanate, which was then regarded as an 
inorganic compound, showed that, in the production of this 
substance at least, no vital force was necessary, and this 
hypothetical agency soon after disappeared from the theories 
of the science. Shortly after Wohler's discovery, cyanic 
acid was itself prepared from the elements, and thus the 
synthesis of urea was made complete. 



CYANOGEN AND CARBONIC ACID 189 

Urea is a colorless, crystalline solid of cooling taste. It 
is very soluble in water, and shows the reactions of the acid 
amides. As it contains two amino groups, it is perhaps a 
little more basic than most substances of this class, and 
forms salts with acids. The nitrate is soluble only with 
considerable difficulty in water, and it is customary to take 
advantage of this fact for the purpose of isolating urea from 
urine. With nitrous acid, urea reacts as might be expected, 
forming carbon dioxide, water, and nitrogen: 

/NH 2 
CO +2 HN0 2 = 2 N 2 + 2 H 2 +C0 2 . 

X NH 2 

With the hypobromites of the alkali metals it reacts in the 
sense of the following equation : 

/NH 2 

CO +3 KOBr +KOH = 3 KBr +2 H 2 +KHC0 3 + N 2 . 

X NH 2 

This reaction furnishes a convenient method for its quanti- 
tative determination, the volume of nitrogen gas evolved 
serving as a measure of the urea present. 

URIC ACID AND ITS DERIVATIVES. 

A complicated substance which may be considered as a 
derivative of urea, and which has perhaps as much im- 
portance to the physiologist as the latter, is uric acid. This 
substance seems to play the same role in the organism of 
birds and reptiles that urea does in that of mammals. The 
half-solid excreta of the former are largely made up of uric 
acid. It is also present normally to a slight extent in the 
urine of mammals, and in pathological conditions its forma- 
tion throughout the organism may be very much increased. 
It is a white solid, soluble with great difficulty in water. It 



<. 



* 



190 OUTLINES OF ORGANIC CHEMISTRY 

frequently appears in renal calculi, and it is the essential 
ingredient of the concretions deposited in the joints in the 
disease of gout. Rheumatism is generally attributed to an 
excessive quantity of uric acid in the system, and con- 
sequently solvents of uric acid, such as lithium salts or 
piperazine derivatives, are frequently prescribed as remedies 
in the treatment of this disease. 

The constitution of uric acid is expressed by the following 
formula: 





tfW**4 Sflfif 


NH-C=0 


! */ bCL 


/ 1 


it, S<- 1«* 


CO C-NH 




\ II ^co, 

NH-C-NKT 


> tv *c^tf 





which has been satisfactorily established by several synthe- 
ses. There is a large number of substances of considerable 
physiological importance which have analogous constitutions. 
These may all be regarded as derivatives of a substance 
called purin, 

(6) 
(1) N = CH 
/ I (7) y H 

(2) HC (5) c- n; 

^ II ^CH (8), 

(3) N-C-N^ 
(4) (9) 

and the scientific nomenclature of the group is fixed with 
this relationship in mind. Uric acid itself is called 2.6.8 
trioxypurin. The numbers designate the position of the 
oxygen atoms in the molecule as referred to the carbons 
and nitrogens in purin. It is customary to assign to these 
various atoms the numbers indicated in parentheses in the 
above formula. A discussion of the ways in which the 
position of the substituting groups is determined would take 
us far beyond the limits of a work of this kind. We shall 



CH 3 




\ 

N 


-CO 


C 


1 
c- 


\ 
N 


II 
-c- 


CH 3 


Caffein 



CYANOGEN AND CARBONIC ACID 191 

have opportunity to become acquainted with somewhat simi- 
lar methods of reasoning later on. 

Only two other purin derivatives will be considered here. 
They are 1.3.7 trimethyl-2.6 dioxypurin or caffein, and 3.7 
dimethyl-2.6 dioxypurin or theobromin: 

H 
\ 
N-CO 
/CH 3 /I CH 3 

-N' . = C C-N' 

^CH \ II ^CH 

N^ N-C-N^ 

CH 3 

Theobromin 

The former is the stimulating principle found in tea and 
coffee. The latter is found in cocoa. Its physiological action 
is much like that of caffein. 



CARBON BISULPHIDE. 

Carbon bisulphide may be considered as an analogon of 
carbon dioxide, and this is borne out by much of its chemi- 
cal behavior. It is usually prepared by the action of sulphur 
upon hot coals. The product is a colorless oil, heavier than 
water, which boils at 47°. It has a high refractive index as 
well as high dispersive power, and in consequence it is some- 
times used to fill prisms designed to show a much elongated 
spectrum. Technically it is much employed as a solvent. 
Among other things it readily dissolves phosphorus and 
sulphur, and so is used in the vulcanization of rubber. The 
vapors of carbon bisulphide are spontaneously inflammable 
when in contact with the air at a temperature of 149° — a 
temperature sometimes reached by a pipe containing steam 
under pressure. This fact should be borne in mind by those 
who have occasion to work with this substance, especially in 



192 OUTLINES OF ORGANIC CHEMISTRY 

evaporating any quantity of it. It should further be remem- 
bered that a carbon bisulphide fire is a particularly difficult 
one to fight, as the sulphur dioxide formed by the combus* 
tion makes the respiration of the surrounding air intolerable. 
Chemically this substance is quite reactive. The products 
formed may, for the most part, be regarded as derivatives 
of carbonic acid in which more or less of the oxygen has been 
replaced by sulphur. Most of these compounds are not, 
however, of much interest to the non-professional student. 
One reaction which is, perhaps, as well worth mentioning 
as any, is the formation of ammonium sulphocyanate from 
carbon bisulphide and alcoholic ammonia: 

Cf +4NH 3 = C'( +(NH 4 ) 2 S. 

^S X S-NH, 






" i; "Cfj\: 



%5L 



< 



CHAPTER XI. 

THE AMINO-ACIDS AND PROTEINS. 

THE AMINO-ACIDS. 

When chlorine or bromine acts upon a fatty acid, the 
direct substitution of one hydrogen by the halogen is effected. 
With practical uniformity, the hydrogen atom substituted is 
one connected to that carbon atom which stands next to the 
carboxyl group. This is called the alpha carbon atom. What 
happens is shown graphically in the following equation: 

CH 3 CH 3 

I I .H 

ch 3 c' 

I + C1 2 = HC1 + I X CP 

c=o c=o 

OH OH 

and the product in this particular case is called a-chlorpro- 
pionic acid. If such a chlorinated acid be now treated with 
ammonia, a reaction takes place entirely analogous to that 
which occurs when an alkyl halide is treated with the same 
reagent. The halogen is now in its turn substituted by the 
amino-group : 

CI NH 3 

/ / 

CH 2 + 2 NH 3 = NH 4 C1 + CH 2 
\ \ 

COOH COOH 

The product of the reaction just written, aminoacetic acid, 
has properties which are typical of a large class of similarly 
constituted substances and, on that account, deserves more 

193 



194 OUTLINES OF ORGANIC CHEMISTRY 

than passing notice. As will be shown a little later, those 
important constituents of animal tissue, the proteins, stand 
in a close chemical relationship to the amino-acids, and this 
gives to the latter an especial significance. 

Aminoacetic acid is a colorless, crystalline solid very 
soluble in water. For a substance called an acid, it has the 
unusual property of a sweet taste, and to this it is indebted 
for two other names, glycine and glycocoll. The acid can 
be obtained by the action of hydrolytic agents upon glue. 
The acid properties of glycine are not very marked, although 
it forms salts, among others a beautiful copper compound 
which is frequently made use of in purifying the mother 
substance. The formula of glycine gives rise to some inter- 
esting considerations. Obviously it is at once an acjjAjand 
a primary amine, and since compounds of the latter class 
are strongly basic, the neutral character of glycine may be 
accounted for by the mutual neutralization of its constituent 
radicles. This might perhaps be still more clearly expressed 
by ascribing to glycine the structure of an internal salt. For 
this reason the formula, 

NH 3 

CH 2 O 

CO 

is preferred by some chemists. From either formula it is 
easy to predict certain points of chemical behavior which 
are found verified by experience. When the amino-group 
is neutralized by an acid, the nature of the carboxyl group 
makes itself felt, and the salt, 

/ NH 2 , HC1 
CH 2 

x COOH 
is a true acid. On the other hand, when the acidic tendencies 



THE AMINO-ACIDS AND PROTEINS 195 

of the carboxyl group are negated by esterification, the re- 
sulting compound, 

/NH 2 

CH 2 

X C = 

OC 2 H 5 

is a strong base. 

The esters of glycine show another somewhat complicated 
reaction which, on account of the important consequences 
involved, deserves special attention. When the ethyl ester, 
for example, is allowed to stand in aqueous solution, two 
molecules of alcohol are liberated, and the corresponding 
glycine radicles unite to form a bimolecular cyclic anhydride 
as indicated by the following equation: 

NHH C 2 H 5 -0-C = NH-CO 

/ \ / \ 

CH 2 + CH 2 = 2C 2 H 5 OH+CH 2 CH, . 

\ / \ / 

COOC 2 H 5 HHN CO-NH 

This substance belongs to a class of compounds called pipera- 
zines which otherwise have no further interest for us. The 
important thing to remember about them is the fact that 
by the action of gentle hydrolytic agents, the ring may be 
split at one point as shown in the following equation: 

NH, 





/ 


/CH 2N 


CH 2 
1 


CO NH 


CO 


1 h -+H 2 = 


= 1 


NH CO 


NH 


\ / 


1 


CH 2 


CH 2 



COOH 



196 OUTLINES OF ORGANIC CHEMISTRY 

The product deserves special attention. It will be noted 
that it is a glycine, 

/NH 2 



CH 2 

CO 



L 2 
\ 



in which one hydrogen of the amino-group has been sub- 
stituted by a second glycine radicle. In consequence, the 
compound is named glycyl-glycine. The method just out- 
lined was historically the first of several by which it has been 
found possible to combine molecules of the amino-acids in 
long chains. The complex substances thus formed need 
not necessarily consist of a single amino-acid as in the case 
just cited. On the contrary, products containing quite a 
large number and variety of components have been synthe- 
sized. The system of nomenclature applied to such products 
and the number of isomers possible can best be made clear 
by a few illustrations. 

The next higher homologue of glycine, aminopropionic 
acid, is commonly called alanine: 

CH 3 

I V NH 2 
COOH 

It is obvious that this substance can be combined with gly- 
cine in such ways as to form two different products: 

CH 2 - NH 2 CH 3 - CH - NH 2 

I I 

CO CO 

)NH and )NH * 

CH 3 -CH CH 2 

I I 

COOH COOH 



THE AMINO-ACIDS AND PROTEINS 197 

These are called respectively glycyl-alanine and alanyl- 
glycine. It must further be borne in mind that alanine 
contains an asymmetric carbon atom (indicated in the for- 
mula by an asterisk). It follows from this that each of 
the two above formula? must represent two optically active 
forms which are to be distinguished in the first case as 
glycyl-d-alanine and glycyl-Z-alanine, and in the second as 
d-alanyl-glycine and Z-alanyl-glycine. As a further example, 
a more complicated case may be cited. Aminoisovalerianic 
acid is known as valine and aminoisocaproic acid as leucine: 

CH 3 CH 3 CH 3 CH 3 

CH CH 

c' CH 

I X NH 3 | H 

COOH C ' 

I NH 3 
COOH 

Valine Leucine. 

Now let it be supposed that several molecules of the four 
amino-acids just mentioned are combined into a complex 
having the formula indicated on the following page. In 
this formula the asterisks indicate the asymmetric carbon 
atoms, and the dotted lines mark off the portions of the 
compound originally belonging to each amino-acid. The 
name of this compound would be valyl-leucyl-alanyl-leucyl- 
dialanyl-glycine . The number of possible isomers which 
might exist when we consider all the asymmetric carbon 
atoms as well as all the possible permutations in the 
order of the different amino-acids might be an attractive 
problem if the exact numerical result had any real interest 
for us. As it is, the question is raised only to arrest the 
attention and convince the student that the number is 
extremely large. Another important fact concerning the 



198 



OUTLINES OF ORGANIC CHEMISTRY 



w 

w w 8 

£ — o — o 





1 
o-o-w 

w 






*4- 

* 1 
52; 


w 

o 


i 

« o =o 
W ' 
-o-o-W 
* i 

W 




« 0=0 

o-o-W 
* i 






O 
o 

e, I 

o — o* 
i 

w 









o 
o 



THE AMINO-ACIDS AND PROTEINS 199 

complex substances of this type is that they all, when 
treated with energetic hydrolytic agents, are split again 
into the same amino-acids from which they were originally 
built up. In the case of the compound cited, molecules of 
water would be added in such a way as to cause splitting 
at the points indicated in the formula by the dotted lines, 
and the products in this case would be two molecules of 
leucine, one of valine, one of glycine, and three of alanine. 
This particular compound is imaginary, but the formation 
of such structures should not be considered as at all beyond 
the limitations of practical synthesis. Indeed Emil Fischer, 
the pioneer in this field, has already been able to build up 
compounds of this type which on hydrolysis yielded no less 
than twelve molecules of amino-acids. He calls all such 
complexes polypeptides, a name whose significance will 
presently appear. 

THE PROTEINS. 

The proteins, frequently spoken of as albumins, are the 
extremely important substances which make up the principal 
portion of the animal tissues, such, for example, as the skin, 
hair, nerves, muscles, and the bulk of the internal organs. 
Among the proteins which may reasonably be concluded to 
represent true chemical individuals are the material of the 
white of egg, casein from milk, keratin from horn, fibroin 
from silk, gelatin from cartilage. As will be seen at once, 
these substances show wide differences in physical proper- 
ties. It is therefore at first sight rather surprising to find 
that they exhibit so narrow a range of percentage composi- 
tion. This is shown in the accompanying table. 

Carbon 50 to 55 per cent 

Hydrogen 6.9 " 7.3 

Oxygen 19 "24 

Nitrogen 15 "19 

Sulphur 0.3 " 2.4 " 



200 OUTLINES OF ORGANIC CHEMISTRY 

Very few of these albuminous substances can be obtained 
in a crystalline form, and the usual criteria of purity are 
lacking in most of them. Further, they usually form only 
colloidal solutions, and are easily affected or totally altered 
in physical properties by changes of temperature. The 
white of an egg, and the way in which it is affected by heat, 
will serve as a familiar illustration. Properties like this 
naturally make it a difficult matter to determine the molec- 
ular weights of these substances, and no thoroughly reliable 
measurements have been made. Some idea of their molec- 
ular magnitude can be obtained from reasoning like the 
following: — Almost all substances of this class contain sul- 
phur. This is usually present in small quantities of which 
it would probably be fair to call one per cent a fair average. 
Now upon the assumption that a molecule of a protein 
containing one per cent of sulphur contains one atom of that 
element, a minimum value for its molecular weight would 
be arrived at by the proportion, 

1 : 100 : : 32 : 3,200. 

Similarly, there is an important albuminous substance in 
the blood called haemoglobin. It contains iron, which is 
certainly not an impurity, though it makes up but 0.40 % 
of the compound. A similar proportion gives, 
0.4 : 100 : : 56 : 14,000, 

and this is in fair agreement with such direct determinations 
as have been attempted. It will be seen that, in any case, 
the molecular weight must be very high, and this is in line 
with what might be expected from properties of the sub- 
stances concerned. 

The key to the chemical character of the proteins is fur- 
nished by their behavior upon hydrolysis. By such ener- 
getic means as protracted boiling with dilute acids, they 
may be decomposed almost quantitatively into a mixture 



THE AMINO-ACIDS AND PROTEINS 



201 



of about twenty amino-acids. Almost all of these acids 
are produced by the hydrolysis of every protein, but the 
proportions of each which are formed vary widely in differ- 
ent cases. Thus, fibroin from silk yields 36 % glycine, 
whereas keratin from horn gives only a trace. If ferments 
are used instead of acids, the reaction proceeds in stages, 
and more or less well-marked intermediate products can be 
obtained. These have received various names, such for 
instance as albumoses, peptones, and the like, but it is now 
very doubtful whether these represent true chemical indi- 
viduals. It is rather probable that they are analogous to 
the dextrins which appear as intermediate products in the 
hydrolysis of starch. In their turn, the albumoses and 
peptones, whatever their chemical nature, yield amino- 
acids on further hydrolysis. The names and formulae of the 
amino-acids usually met with as components of albuminous 
substances will be found in the accompanying table. 



/ NH 2 
CH 2 



\ 



COOH 



Glycine 



H 2 C-OH 



CH 3 
I 
H-C-NH 2 
I 
COOH 

Alanine 



CH 3 CH 3 
\/ 
CH 
I 
H-C-NH 2 
I 
COOH 

Valine 



CH, CH 3 
\> 
CH 
I 

CH 2 
I 
H-C-NH 2 
I 
COOH 



CH 3 
I 

CH 2 CH 3 
\/ 
CH 
I 
H-C-NH, 
I 
COOH 



Leucine 



Isoleucine 



COOH COOH COOH 

I I I 

C-NH 2 H-C-NH 2 H-C-NH 2 H-C-NH 2 



I 
COOH 

Serine 



CH 2 
I 
COOH 

Aspartic 
acid 



I 

CH 2 

I 
CH 2 

I 
COOH 

Glutamic acid 



I 
CH 2 

I 
CH 2 

I 
CH 2 

I 
H 2 C-NH 
Lysine 



/NH 2 

C=NH 
V 



/ 



NH 



CH a 

I 



CH 2 
I 
CH 2 

I 
2 H-C-NH 
I 
COOH 

Argenine 



Diamino- 

trihy- 

droxy- 

2 dodecylio 

acid 



202 



OUTLINES OF ORGANIC CHEMISTRY 



Some of the following compounds contain aromatic radi- 
cles, but as we are not now concerned further with their 
specific properties, their introduction at this point need 



ause no confusion 

CH 2 -S-S-CH 

■ 1 


i 


H 2 C-OH 

l 


ps> 




OH 


H-C-NH 2 H-C- 


NH 2 


H-C-OH 




1 


u 


COOH COOH 

Cystine 


H-C-OH 

1 
H-C-OH 




u 

CH 2 


CH 2 
1 
H-C-NH 2 


, 




H-C-NH 2 

1 
H-C = 

Glucosamine 


H-C-NH 2 
1 
COOH 

Phenyl alanine 


COOH 

Tyrosine 


I^C-CH, 

1 1 
H 2 C CH 

^ V QOOH 

Proline 


H 

1 

H 2 C-C-OH 

1 1 
H 2 C CH 

NH XC00H 

Hydroxy-proline 


H 
H 


-C=C— — CH 

1 1 1 
-N N H-C-NH, 

\S 1 
CH COOH 

Histidine 




y^u^i tM v" 



u 



c- 



CH< 



II H-G-NH, 
CH COOH 



NH 

Tryptophan 



When albuminous substances are subjected to especially 
cautious hydrolysis by the means of ferments, it has been 
found possible to isolate from the reaction mixture certain 
products i jcvhich are identical with synthetic polypeptides. 
Conversely, it has been found in the synthesis of the latter 
compounds that as the molecular weight and complexity 



THE AMINO-ACIDS AND PROTEINS 203 

increased, the physical and chemical properties observed 
became more and more like those of the natural peptones. 
This not only serves to show the appropriateness of the name 
" polypeptides," but it furnishes substantial evidence that 
the albumins themselves are essentially polypeptides of 
great complexity and high molecular weight. 

Until a natural albuminous substance has been synthe- 
sized, such evidence still falls short of absolute proof, but it 
is obvious that it must be some time before such a synthesis 
can be effected. The great practical difficulties which lie 
in the way will be partially realized from a study of the 
number of possible isomers suggested by the formula of the 
imaginary (yet in comparison with the natural proteins ex- 
tremely simple) polypeptide mentioned on page 198. For 
the present, the general chemical character of albuminous 
substances can be regarded as qualitatively well established. 

CASEIN. 

No attempt will be made to give a description of the 
numerous individual substances usually classed as proteins, 
though some of them possess great physiological interest. 
Casein, however, has recently become an article of commerce, 
and has found use in a variety of ways; as a sizing for paper, 
as a constituent of glues and cements, as a waterproofing 
material, in substitutes for celluloid, etc. The source of 
casein is milk. It may be precipitated from this solution 
by the addition of a little dilute acid. Precipitation may 
also be brought about by the ferment of the rennet; thus, 
as its name indicates, casein is the chief constituent of 
cheese. It may be purified by re-solution in dilute alkalies 
and precipitation with acid. Thus prepared, casein is a white 
amorphous powder which on hydrolysis yields about 10 % 
each of leucine and glutamic acid, with smaller quantities of 
the other amino-acids. 



CHAPTER XII. 

ORGANIC CHEMISTRY OF CERTAIN VITAL PROCESSES. 

It has already been shown that organic compounds need 
not owe either their formation or preservation to any mys- 
terious forces connected with the living cell, but that their 
syntheses and reactions depend upon the play of the same 
physical and chemical influences which are active in the 
inorganic field. This should not blind us, however, to some- 
thing else which is equally true. Though it has proved 
possible, for example, by all the resources of a well-equipped 
laboratory, to prepare a small amount of grape sugar from 
the elements by the action of numerous reagents and much 
complicated apparatus, nevertheless this achievement has 
done surprisingly little toward revealing the method by 
which nature accomplishes similar results. With no material 
to work with except water, the gases of the atmosphere, and 
dilute salt solutions obtained from the moist soil, the plant 
is able at ordinary temperatures to produce, often in sur- 
prisingly large quantities, such complicated substances as 
cane sugar, starch, cellulose, chlorophyll, and the vegetable 
alkaloids, — substances which still stand beyond the reach 
of laboratory synthesis. How these results are attained is 
still practically unknown, though it has been possible to get 
glimpses of the mechanism of certain processes here and 
there. The importance of making an attempt to get an 
answer to such questions lies in the fact that life itself, at 
least upon the vegetative and mechanical sides, is essentially 
a chemical process. The digestion of the food, the con- 
traction of the muscles, even the action of the brain cells, 

204 



ORGANIC CHEMISTRY OF VITAL PROCESSES 205 

are all doubtless accompanied by chemical changes, and 
depend for the energy necessary for their execution upon 
chemical reactions. As these reactions take place largely 
between organic substances, the problems involved have a 
proper and natural interest for organic chemists, though 
hitherto the latter have largely contented themselves with 
studying the products in the laboratory, instead of attempt- 
ing to discover what goes on within the organism. The 
latter subject has developed into a special branch of the 
science called Physiological Chemistry. It is the aim of 
this department of science to trace the transformations 
undergone by the chemical elements from the time when 
they are first assimilated into a living organism until they 
are again eliminated from it. This involves as an ultimate 
goal the discovery of all the changes which go on in every 
kind of living cell, the character of the products, and the 
ways in which the activity of the cell is affected by all the 
chemical influences which can be brought to bear upon it. 
It is needless to say that only the first steps have been taken 
toward carrying out so ambitious a program. Much in- 
teresting work has, however, been done, and many impor- 
tant generalizations are under discussion. Nevertheless the 
inherent difficulties of animal experimentation are so great, 
and the whole subject really so new, that there still exists 
wide divergence of opinion among the experts even concern- 
ing fundamentals. This state of things makes it clear 
enough why no very full presentation of the subject can be 
attempted here. What is included will only be a few points 
having mainly to do with nutrition. These are discussed 
partly on account of their general interest, and partly to 
direct the attention of the student of Biology to the numer- 
ous and increasing points of contact between that science 
and Organic Chemistry. It will be necessary to abandon 
any attempt at a critical presentation of the material, and 



206 OUTLINES OF ORGANIC CHEMISTRY 

to content ourselves with simple and perhaps seemingly 
dogmatic statements of what the author understands to 
represent the consensus of expert opinion at the present 
time. 

With the exception of certain parasitic and so-called car- 
nivorous species, plants depend entirely upon inorganic 
material for their nourishment. They absorb carbon di- 
oxide from the air, and dilute salt solutions through their 
roots from the soil. Perhaps the most important constitu- 
ents of this solution are the nitrates and nitrites, from which 
the plant must get practically its Whole supply of nitrogen. 
A few other inorganic salts in small quantities seem to be 
necessary to the life of the plant. Phosphates, potassium 
and calcium salts should be mentioned as perhaps the most 
important of these. The organic compounds which the 
plant builds up fall, for the most part, into three classes : — ■ 
the carbohydrates, — mostly monoses, starch, and cellu- 
lose; — the fats, — materials like cotton oil, palm oil, lin- 
seed oil, and the like; — and certain protein materials, found 
mostly in nuts and seeds. It will be understood that the 
plant also produces many substances belonging to other 
classes, like the acids in fruits, the terpenes in coniferous 
trees, the alkaloids in various poisonous plants. The three 
classes first mentioned are, however, entitled to be con- 
sidered as most important, partly because their production 
is most general, and partly because they serve the animal 
organism as foods. The synthesis of these organic com- 
pounds from carbon dioxide is a reduction process. When 
organic material, wood (cellulose) for example, is burned, 
heat is evolved. This means that if cellulose is, in its turn, 
to be prepared from carbon dioxide, energy must be fur- 
nished. This energy comes from the sun. Plants, as a 
rule, flourish only when they receive a certain amount of 
sunlight, and under these conditions they absorb carbon 



ORGANIC CHEMISTRY OF VITAL PROCESSES 207 

dioxide through the leaves and give off oxygen. For the 
animal, on the other hand, carbohydrates, fats, and proteins 
constitute the nourishment, and these are oxidized by the 
organism, forming, in the case of mammals, carbon dioxide, 
water, and urea. The solar energy which the plant had 
stored up is now set at liberty, partly as animal heat, and 
partly in the form of mechanical work, using this term to 
include not only the muscular activity and locomotion of 
the animal, but also the work done in carrying out the vital 
functions within the organism. This brings out the curious 
unconscious partnership existing between plant and animal 
life taken as a whole, — the animal absorbing oxygen and 
evolving carbon dioxide, while the plant exercises the 
reciprocal functions. A similar mutual relationship exists 
in what is often spoken of as the " nitrogen cycle." 

Neither plant nor animal- can, as a general rule, make 
direct use of the nitrogen of the atmosphere. Plants derive 
practically all their supply from the nitrites and nitrates in 
the soil. Herbivorous animals get theirs from the proteins 
of the plant; carnivora from the herbivora which they 
devour. The nitrogenous excreta of animals, after leaving 
the body, usually go over rapidly into ammonia, and, in 
this form, the nitrogen is not available for The plant. By 
the aid of certain bacteria, however, oxidation to nitrite or 
nitrate can be brought about and the nitrogen becomes 
available. In the course of this oxidation a good deal of 
the valuable material is lost as gaseous nitrogen. In com- 
pensation, there exist, among other agencies, certain organ- 
isms parasitic upon leguminous plants, which are able to 
so utilize the nitrogen of the air that a soil which has 
been planted with this kind of vegetation becomes richer 
in nitrogen. 

When we come to trace the organic side of vegetable 
processes in a little more detail, we encounter at the outset 



208 OUTLINES OF ORGANIC CHEMISTRY 

the difficulty that the metabolism (internal chemical change) 
of the plant is even less clearly understood than that of the 
animal, and the very first step made by the plant in building 
up its carbon compounds is perhaps the darkest chapter 
in the whole series. The absorption of carbon dioxide in 
the leaves is carried on through the agency of chlorophyll, 
an exceedingly complicated substance to which the leaf 
also owes its green color. The mechanism of the action of 
chlorophyll is not understood, nor is there any certainty 
as to what the first product formed by the reduction of the 
carbon dioxide may be. It is, however, generally agreed 
that carbohydrates are formed at an early stage. In fact, 
the carbohydrates seem to play the most important role in 
the plant's economy: — cellulose is the chief constituent of 
its tissues, sugars circulate in its sap and are found in its 
fruits, while its reserve supplies are mostly stored up in the 
form of starch. 

A number of years ago, Baeyer proposed a theory which 
is very attractive chemically, but which, in spite of the long 
time which it has been under discussion, can by no means 
lay claim to being proved. This theory assumes that, under 
the catalytic influence of chlorophyll, the first reaction to 
take place produces formaldehyde: 

2 C0 2 + 2 H 2 = 2 HCHO + 2 . 

As was stated when the properties of this substance were 
discussed, only slight traces of formaldehyde have ever been 
found in plants, — in fact this substance acts as a vigorous 
poison upon vegetable organisms. It is therefore necessary 
to make the further assumption that the formaldehyde first 
formed is immediately utilized in the synthesis of more 
complex products. Certainly carbohydrates are soon formed, 
and it is known from laboratory investigations that sugars 
can be prepared by the polymerization of formaldehyde. 



ORGANIC CHEMISTRY OF VITAL PROCESSES 209 

Once the monoses have been reached, the problem begins 
to look a little simpler. It is easily credible that these 
should further condense and polymerize to form such com- 
pounds as the bioses, starch, and cellulose. It is true that 
hardly a beginning has been made toward carrying out 
such syntheses in the laboratory, but that the organism 
does synthesize the higher carbohydrates from the "lower 
admits ofno doubt. It is entirely safe to conclude that the 
starch Mid cellulose of the plant are formed from the monoses. 
Concerning the formation of the vegetable fats and proteins 
little is known. Whether these are to be considered as 
built up directly from formaldehyde, — admitting this to 
be the primary organic substance produced by the plant, — 
or whether they owe their formation to secondary reactions 
of the carbohydrates, is a question to which at present no 
definite answer can be given. It may be noted that stearic 
and oleic acids each contain eighteen atoms of carbon, 
whereas glycerin contains three, and some of the more im- 
portant and common amino-acids which go to make up the 
albumins contain three or six carbon atoms. This might 
suggest that such components of the fats and albumins were 
formed by the combining and splitting of the common 
hexoses. This is, however, little better than idle specula- 
tion. Well-established intermediate steps are wanting. 

At this point the student may well ask how it is that it is 
ever possible to predicate that the cell performs this or that 
chemical reaction, for which on the basis of ordinary labora- 
tory experience the necessary conditions seem to be wanting, 
or where the reaction (as for example the synthesis of 
cellulose) cannot be carried out in the laboratory at all. 
The answer is that in some cases the question can be ap- 
proached by direct experiment. Thus if blood containing 
both benzoic acid and glycine be circulated through the 
kidneys of a freshly killed animal, hippuric acid is formed. 



210 OUTLINES OF ORGANIC CHEMISTRY 

This is very satisfactory evidence that the synthetic 
reaction, 

C fl H 5 COOH+ H 2 N • CH 2 . COOH = 

H 2 +C 6 H 5 CO • NH • CH 2 . COOH, 

which cannot be carried out in the laboratory at ordinary 
temperature, is effected in some way by the cells of the 
kidney. Perhaps more frequently the evidence is not as 
good as this. The well-known fact, however, that many 
reactions take place in the laboratory when the assistance 
of certain enzymes is available, which would not go on 
outside the organism without such assistance, leads us to 
believe that the cell produces one compound from another 
if certain conditions are fulfilled. Thus the presence of 
both in the organism should be assured, the constitutions 
of the two should stand in such relation that the reaction 
itself looks reasonable, and, in general, it should be shown 
that the quantity of one substance grows as the other de- 
creases. Of course it must be admitted at the outset that 
evidence of this kind only leads to more or less temporary 
conclusions, and that the physiological chemist is under 
obligation not to be content with this, but to verify it by 
experiments bringing to light the greatest possible number 
of intermediate steps, either in the laboratory or in the 
organism. 

When we turn to the subject of animal nutrition, the 
relations are somewhat better studied and therefore a little 
more clearly traced. Of the three classes of foods utilized 
by the animal, the carbohydrates are perhaps the best to 
begin with. Most carbohydrate nourishment is taken in 
the form of starch. Following starch, then, in its course 
through the digestive tract, we find that in the mouth it 
first becomes mixed with the saliva. This secretion con- 
tains a ferment called ptyalin jwhich has the power of be- 



ORGANIC CHEMISTRY OF VITAL PROCESSES 211 

ginning a hydrolytic action resulting in the formation of 
dextrins and a little maltose. These, together with the 
unhydrolyzed portions of the starch, pass, mixed with the 
saliva, into the stomach. Whatever hydrolysis takes place 
here is due to the continued action of the saliva, for the 
secretions of the walls of the stomach do not act upon starch. 
In the duodenum, however, the dextrins are acted upon by 
diastatic ferments secreted by the pancreas. These further 
hydrolyze them into the component monoses. These, ab- 
sorbed by the intestinal wall ,~p ass By^vay of the portal vein 
and the liver into the blood. Now the liver, in addition to 
several other important functions, acts as a regulator for 
the carbohydrate nourishment of the body. The way in 
which it does this has been an object of much study and is 
extremely interesting. It is well known that the livers of 
those animals used as food have a sweet taste. This is due 
to the presence of d-glucose. Nevertheless if the animal be 
killed, and the liver at once removed and examined, it will 
be found to contain no glucose, but a substance resembling 
starch. This is glycogen, sometimes called "animal starch." 
It gives a brownish red instead of a blue color with iodine, 
but upon hydrolysis, like the vegetable product, it yields 
d-glucose. The fact that this hydrolysis takes place spon- 
taneously soon after the death of the animal shows that a 
suitable hydrolytic ferment must be present in the liver 
cells themselves. Many experiments have conclusively 
shown that the organism depends normally in large measure 
upon its carbohydrate nourishment for the performance of 
muscular work. Further it is known that the muscles con- 
tain some glycogen as well as the liver, and that the sugar 
content of the blood is small but extremely constant even 
under wide variations of diet and exercise. These facts 
taken together furnish data for a consistent theory of car- 
bohydrate metabolism. This may be outlined in general 



212 OUTLINES OF ORGANIC CHEMISTRY 

terms as follows: d-Glucose is the form in which carbo- 
hydrate nourishment is transported and glycogen the form 
in which it is stored. The liver takes up monoses produced 
by the digestion of starch and other carbohydrates, and 
from them forms glycogen, except for a certain minimum of 
d-glucose which circulates in the blood. When a muscle 
contracts, the nerve stimulus doubtless releases at the same 
time a ferment which hydrolyzes some of that muscle's 
glycogen, the d-glucose formed being oxidized to furnish 
the energy required for the contraction. The muscle then 
recoups itself by taking up glucose from the blood, and the 
sugar concentration of the latter is in turn kept constant by 
the action of the liver, which hydrolyzes enough of its own 
store of glycogen to replace the deficit. An interesting con- 
firmation of these views is found in the fact that the livers 
of animals which have been kept a long time without food 
contain no glycogen. 

If the organism receives a larger quantity of carbohydrate 
than it requires, it seems to have the power of transforming 
this into fat, but the chemical stages by which this is accom- 
plished can, for the present, only be guessed at. 

The fats represent that portion of the nutriment which 
is most valuable for the maintenance of the temperature of 
the body, since the combustion of fat furnishes, per unit of 
weight, more heat than the oxidation of either carbohydrate 
or protein. The fats are not appreciably acted upon by the 
saliva or by the gastric juices. In the duodenum, however, 
they come under the influence of a ferment called lipase. 
Here the fat becomes very finely divided and a part of it at 
least is hydrolyzed into fatty acids and glycerin. The fact 
that during the digestion of fat the chyle becomes milky 
with fat globules has led to some controversy as to whether 
the larger part of the fat is saponified by the process of 
digestion, then absorbed, and finally recombined, or whether 



ORGANIC CHEMISTRY OF VITAL PROCESSES 213 

in a fine emulsion it passes without hydrolysis through the 
intestinal wall. This controversy need concern us little 
here since it is well known that some hydrol^sis_does take 
place, ami also that the organ ism does~have the power of 
synthesizing fat. Experimental evidence on this point is 
to be found in the fact that animals deficient in fat increase 
their supply when they are fed upon fatty acids. In this 
case the organism must itself furnish the necessary glycerin, 
but from what source this is derived is not known. 

An interesting side-light is thrown on the assimilation of 
the fats by the experiment described below. It is a familiar 
fact that the fat deposits of the various animals consist of 
varying, but for a given species characteristic, proportions 
of the oleate, palmate, and stearate of glycerin. Olein 
being liquid at ordinary temperatures, while stearin and 
palmitin are solids, the melting point of a given fat becomes 
a characteristic constant for the animal species from which 
it is derived. Now a dog (whose fat melts at about 20°) 
was starved till his fat deposits were nearly exhausted, and 
then fed freely with fatty acids formed by saponifying 
mutton fat. This melts at about 40°. It was found by 
post-mortem examination that the animal experimented 
upon had laid on fat melting at 40°. This seems to indicate 
that the organism was in such extreme need of fat that it 
used the acids provided without chemical transformation. 

Such an experiment shows what the organism is capable 
of doing under certain, for the animal involved, desperate 
conditions. It is always doubtful how much light such 
experiments throw upon what the organism normally does 
under healthy conditions. For this reason, conclusions 
drawn from experiments upon living animals should always 
be received with caution, especially where the animal experi- 
mented upon is subjected to operations involving great ner- 
vous shock or extensive derangement of its vital processes. 



214 OUTLINES OF ORGANIC CHEMISTRY 

We now come to the consideration of the albuminous 
contents of the food. It has already been pointed out that 
these probably represent long chains of amino-acids con- 
densed somewhat in the manner suggested upon page 198. 
In the acid digestion of the stomach, these are broken down 
into the albumoses and peptones. These we are again to 
consider as polypeptides of uncertain but, for the most part, 
high molecular weight. In the small intestine the food is 
subjected to the action of aj ^aline f erments. Predominant 
among these is tr ypsin, contained in the secretion of the 
pancreas. Here the hydrolysis is completed and the prod- 
ucts absorbed. Amino-acids are certainly formed. Whether 
other partially hydrolyzed fragments like the polypeptides 
are absorbed without complete hydrolysis has not been 
settled with certainty. The evidence seems to indicate 
that the organism can at least make use of certain larger 
fragments. 

The organism transforms so rapidly the albuminous prod- 
ucts which it absorbs, that it has hitherto been found impos- 
sible to trace any steps in the process. Upon the other side 
of the intestinal tract there can be found neither albumoses, 
peptones, nor amino-acids. Instead, the intestinal wall has 
already synthesized the material which it has absorbed into 
proteins characteristic of the organism itself and not of the 
foods. The blood thus comes to contain its own proteins, 
which are characteristic of the animal species and do not 
depend qualitatively upon the kind of albumins in the food. 
This gives to the tissues an essentially constant and uniform 
source of nutrition. From the blood-stream the cells appar- 
ently take up such proteins as they require, split them under 
the action of specific ferments to a certain extent, and build 
them up again into that form of albumin required by the 
particular cell. These processes must be very complex, and 
their mechanism is little understood. How far reaching the 



ORGANIC CHEMISTRY OF VITAL PROCESSES 215 

changes must be is suggested, for example, by contrasting 
the physical properties of the hair and nails with the globulin 
of the blood. 

In comparing the three chief classes of organic foods, it 
should be pointed out that it is possible to sustain life solely 
upon albuminous material. Further, it is impossible to 
maintain life without a certain minimum of this class of 
nourishment. One reason of this appears when it is con- 
sidered that the organs are chiefly made up of this albuminous 
material, and the wear and tear upon them can be made 
good in no other way. A certain amount of protein can, 
however, be profitably substituted by fats and carbohydrates, 
and it is for the advantage of the organism to employ a 
mixed diet where this is practicable. It is an interesting 
fact that while, if the diet contains an excess of fat, this 
is stored up, and the same holds true to a limited extent 
of carbohydrates, this is not the case with protein. Here 
the rule is that in a healthy individual, the nitrogen ex- 
creted in a given time is equal to the amount present in the 
nourishment. When this is true, the animal is said to be 
" in nitrogen equilibrium." In mammals almost all of the 
nitrogen is excreted in the form of urea. This accounts, 
of course, for but one carbon atom in the molecule of each 
amino-acid. What becomes of the rest of the chain is not 
known. It may be oxidized directly, or it may be used for 
the synthesis of fats and carbohydrates. When an animal 
is existing upon an exclusively protein diet, the latter would 
seem more probable. Perhaps the material is available in 
a variety of ways, according to the temporary needs of the 
organism. 

In addition to the foods previously considered, the organ- 
ism also requires large quantities of oxygen, of water, and 
much smaller but essential minima of certain inorganic 
salts, notably sodium chloride. The functions of the salts 



216 OUTLINES OF ORGANIC CHEMISTRY 

are not perfectly understood, though it is known how impor- 
tant for the vital processes are certain osmotic effects in the 
walls of various organs. The role which salt solutions play 
in stimulating and maintaining-the pulsations of the heart, 
as well as in certain forms of parthenogenesis would be fasci- 
nating topics, but these are contributions made to Physio- 
logical by Physical rather than by Organic Chemistry. 

THE BLOOD. ", 

It is by means of the blood that almost all transportation 
of material takes place between the various organs. It 
brings to the cells the carbohydrates, albumins, and fats in 
such form that they can be appropriated by the cells as 
needed. By means of its corpuscles, it brings oxygen from 
the lungs to the cells, where it may be employed for the 
oxidation of the food material or the tissues themselves; 
and it receives from the cells the products of oxidation, 
taking carbon dioxide back to the lungs whence it is ex- 
pelled in the breath, and the urea to the kidneys whence it 
is discharged in the urine. The various kinds of material 
circulating in the blood, and the functions of each, furnish 
an attractive study, but must for the most part be passed 
over here. A word should perhaps be said concerning the 
important but doubtless familiar subject of oxygen trans- 
portation. ' It has already been pointed out (page 200) that 
the blood contains a material called hcemoglobin which is 
an extremely complicated substance and contains a small 
but essential quantity of iron. Within the lungs, this 
substance has the power of adding directly a certain quantity 
of oxygen, forming oxyhemoglobin. This in its turn gives 
up its oxygen to the tissues as it is needed for oxidation, 
returning again to the lungs for a renewed supply. Haemo- 
globin is of a dark purplish color, while oxyhemoglobin is a 
brilliant red, and this accounts for the well-known difference 



ORGANIC CHEMISTRY OF VITAL PROCESSES 217 

in color between venous and arterial blood. Recent in- 
vestigations go to show that there is a certain analogy in 
constitution between haemoglobin on the one side, and 
chlorophyll on the other." This is extremely interesting, 
since the two substances perform functions which are in one 
sense analogous and in another sense reciprocal. In con- 
nection with the iron content of haemoglobin may also be 
mentioned the interesting fact that in the blood of certain 
mollusks and Crustacea, the substance which performs the 
functions of an oxygen carrier contains copper, and the arte- 
rial blood of such animals is normally blue while the venous 
is colorless. 

It wou].d be Interesting to continue these discussions to 
include the functions of each organ and every secretion, 
but for such topics the student must be referred to special 
treatises upon Physiological Chemistry. 



CHAPTER XIII. 

BENZENE AND ITS HOMOLOGUES. 

THE AROMATIC COMPOUNDS. 

The original meanings of the terms aliphatic and aromatic 
have already been discussed. As now used, the latter 
adjective suggests only certain chemical characteristics. 
Probably the most important of these is the presence in the 
compounds of this group of an especially stable nucleus. 
In the case of the most important group of aromatic com- 
pounds, the benzene derivatives, this nucleus consists of 
six carbon atoms, and the general rule holds that to what- 
ever chemical treatment these Ifubstances are subjected — 
short of complete disintegration or combustion — a com- 
pound containing at least six carbon atoms is one of the 
products. 

In addition to this peculiarity, aromatic substances almost 
always contain several hydrogen atoms which show a capa- 
city for substitution different from that exhibited by hydro- 
gens of the aliphatic compounds. This will be illustrated 
more fully in the description of benzene itself. Finally it 
holds true in a general way that the various classes of aro- 
matic compounds — the halides, the acids, the aldehydes, 
the amines, etc. — show in their chemical character and 
behavior certain well-marked points of difference from the 
corresponding compounds of the fatty series. It would of 
course be premature to attempt to point out these differences 
until the separate classes are taken up individually. 



218 



BENZENE AND ITS HOMOLOGUES 219 

BENZENE. 

The simplest and most thoroughly studied of the aromatic 
compounds is the hydrocarbon benzene. This is a colorless 
liquid of a characteristic aromatic odor which freezes at 6° 
and boils at 80°. Analysis and molecular weight deter- 
minations lead to the empirical formula C 6 H 6 . The com- 
mercial source of benzene is the lower boiling portion of the 
coal-tar distillate. A method of preparation which is very 
interesting scientifically consists in the polymerization of 
acetylene. When that gas is passed through red-hot tubes, 
some benzene is formed: 

3 Co 2 = C 6 H e . 

Transitions of this kind between the aliphatic and aromatic 
series are the reverse of common, and this is one of the most 
important. Further, since acetylene itself can be prepared 
without difficulty from the elements (page 131), this reaction 
completes the synthesis of benzene, and, in consequence, 
that of all the extremely numerous aromatic compounds 
which can be prepared from it. 

When benzene is treated with chlorine or bro mine in the 
presence of certain catalytic agents, all the hydrogen atoms 
may be successively substituted by the halogen: 

C 6 H 6 +C1 2 = HC1 + C 6 H 5 C1, 
C 6 H 5 C1 + C1 2 = HC1 f C 6 H 4 C1 2 , etc. 

This is something like an analogous property of methane 
and its homologues. Here, however, the reaction is much 
more easy to control, so that it is not difficult to isolate the 
several products. 

When benzene is treated with fuming sulphuric acid, the 
following reaction takes place : 

y C 6 H 6 + H 2 S0 4 = H 2 + C 6 H 5 • S0 3 H. 



220 OUTLINES OF ORGANIC CHEMISTRY 

The hydrogen of benzene is replaced by the group S0 3 H. 
This is called the sulpho-group, and the substances pro- 
duced are known as sulphonic acids. Their properties will 
be dealt with later. By the continued action of highly con- 
centrated acid more than one hydrogen may be replaced in 
a similar way. 

If benzene be treated with fuming nitric acid, or with a 
mixture of nitric and sulphuric acids, one or more hydrogens 
are substituted by the nitro-group: 

C 6 H 6 + HN0 3 = H 2 + C 6 H 5 . N0 2 . 

The product of this reaction is called nitrobenzene. Its 
properties are typical of a large and important class of 
compounds. 

Of these four reactions, chlorination, bromination, nitra- 
tion, and sulphonation, the last two are especially charac- 
teristic of the aromatic compounds in general. While it 
is true that all of these reactions may, by special modifi- 
cations, be applied with analogous results to some aliphatic 
compounds, the ease and smoothness with which the reac- 
tions take place in the aromatic series is so striking in 
comparison, that it furnishes a well-marked and useful 
line of distinction. 

In attempting to fix a suitable graphic formula for 
benzene, perhaps the most decisive single fact is that 
but one mono-substitution product is ever obtained by 
any of the above reactions. There exists but one mono- 
chlor-, monobrom-, mononitrobenzene. This indicates that 
all the hydrogens in benzene are chemically equiva- 
lent, and this conclusion has been confirmed by many 
elaborate investigations, the details of which cannot be 
given here. This equivalence finds expression in the 
formula, 



BENZENE AND ITS HOMOLOGUES 221 

H 

I 
C 

/ \ 

H-C C-H 

I I 
H-C C-H 

\ / 

C 

I 
H 

which represents the six carbon atoms connected in a ring, 

and one hydrogen attached to each. It will be noted that 

this formula makes use of but three of the valencies of carbon, 

and many suggestions have been made which attempt to 

fix the position of the additional bond. The original theory 

of Kekule (to whom we are indebted for the ring formula) 

represents the carbon atoms connected by alternate single 

and double bonds: H 

I 
C 

//\ 
H-C C-H 

I II 

H-C C-H 

^ / 

C 

I 
H 

The later theory of Baeyer represents the additional bonds 

as all tending toward the center of the ring: 

H 

H-C( I )C-H 

H-C^ I ^C-H 

X C X 

I 
H 



222 OUTLINES OF ORGANIC CHEMISTRY 

Various other formulae have been suggested, but none have 
found so general acceptance as these two, the relative merits 
of which will be discussed very briefly later. 

Far more important than the disposition of the fourth 
valency is the confirmation of the propriety of using a ring 
formula for benzene, and to this point our attention must 
next be turned. Before beginning the discussion, however, 
a word should be said concerning a system of abbre- 
viation universally employed in practice for the 
formulation of benzene derivatives. This consists in 
representing benzene itself by a simple hexagon, 
concerning which it is conventionally understood that 
each corner represents one carbon atom and the hydrogen 
attached. 

In reading the formula of a substitution product, it is to 
be understood that when a substituting group is attached 
to any corner of the hexagon, that hydrogen has been 
replaced. On the other hand those corners where no 
substituting groups appear continue to stand for carbon 
atoms with their accompanying hydrogen. This will be 
made entirely clear by a single example: 




CH 3 

I 

H-C x N C-H 



CH 



I is abbreviated to 



H-C K /C-NO;, 

I 
Br 




The testing of the ring formula for benzene has been the 
subject of countless investigations, and a whole literature 
has grown up upon the subject. The one argument which 
will be presented here is perhaps the simplest and is suffi- 



BENZENE AND ITS HOMOLOGUES 



223 



ciently convincing. It is also the easiest to retain, because 
the essentials of it can always be derived at will from the 
geometrical properties of the hexagon. The argument con- 
sists first in enumerating the number of compounds which 
can be formed when one element (bromine for example) 
successively substitutes the various hydrogens in a com- 
pound of the formula given; second, in tracing the neces- 
sary genetic relations between such isomers; and finally in 
comparing trie results thus obtained with the observed facts. 
Since the formula represents all the hydrogen atoms as 
equivalent, it can make no difference in the character of 
the product which of them is substituted by a single atom 
of bromine. In other words, but one mono-substitution 
product should be possible, and it has already been stated 
that this is the fact. Turning now to the di-substitution 
products, a brief inspection shows that three dibromben- 
zenes should exist as represented by the folio wing formulae: 

Br Br 



ortho 



Br 

para 



The relative positions occupied by the two bromine atoms in 
the above formulae are known respectively as the ortho, the 
meta, and the para positions. The student should fix these 
terms and their significance very carefully in mind, as the 
words are of constant use in all discussions concerning 
benzene derivatives. When an individual compound is 
referred to it is customary to abbreviate the words to their 
initial letters and prefix these to the name of the compound. 
For example, the name of the substance corresponding to 



224 



OUTLINES OF ORGANIC CHEMISTRY 



the first of the above formulae is written o-dibrombenzene, 
etc. 

Of the tribrombenzenes, there should be three: 



Br 



Br 



Br Br 



vicinal 



symmetrical 




These are called the vicinal, the symmetrical, and the asym- 
metric. There should also be three tetrabrombenzenes, 
and it will be seen at once that the only three possible are 
those which have the unsubstituted hydrogens in the ortho, 
meta, and para positions respectively: 




Br Bi 




Finally it is clear that only one pentabrom- and one hexa- 
brombenzene should be possible: 

Br 





BENZENE AND ITS HOMOLOGUES 225 

Now all the above brombenzenes are known, and it has not 
proved possible to find others, despite the important bear- 
ing which such a discovery would have upon our theoretical 
views. We can go much farther. The same rule holds 
not only for the bromine derivatives but for every case 
where the hydrogens of benzene are substituted by a single 
element or group, so far as the various products involved 
are known. It is not surprising that it should not thus far 
have proved possible to prepare every compound whose 
formula is suggested by the theory. Gaps, however, do 
nothing to vitiate the hypothesis, which only claims to 
state the maximum number of compounds possible. The 
theory gives us further information besides that which has 
been already derived from it. By its aid it is possible not 
only to predict the number of products, but also such genetic 
relations between them as fix with certainty the graphic for- 
mula belonging to each compound. 

Let us consider, in the first place, the three di-substitu- 
tion products. A study of the formula will convince the 
student that from the ortho compound it should be possible, 
by further substitution, to prepare two tri-substitution 
products, the vicinal and the asymmetric: 




ortho 



From the meta compound it should be possible to prepare 
all three tri-substitution products: 



226 OUTLINES OF ORGANIC CHEMISTRY 

iX 
X 







symmetrical 



asymmetric 

xk^ 

X 

From the para only one tri-substitution product, the asym- 
metric, can be obtained: 



o — o 



asymmetric 

^ X 
X Y 

para 

The above discussion gives the necessary data for fixing 
the identity of the three di-substitution products. That 
from which two tri-substitution products can be obtained 
is the ortho compound, that which yields three is the meta, 
that which gives but one, the para. 

Similar reasoning fixes the identity of the tri-substitution 
products, and here additional evidence is furnished by the 
number of tetra-substitution products formed from each. 
Thus the vicinal compound, which is obtained from both 
ortho and meta di-substitution products, may yield in its 
turn two tetra-substitution products which have their un- 
substituted hydrogens in the ortho and meta positions 
respectively: 



BENZENE AND ITS HOMOLOGUES 



227 



ortho 



meta 



-A- H's in ortho 
position 

X 




The asymmetric, which can be obtained from all three di- 
substitution products, can yield, in its turn, all three tetra- 
compounds: 



rtho Q 

X 

x 

neta Q. 

X 

rara I I 



Is^^'X posi 



ortho 
position 



X 
X 



Ox— xOx », 



s m meta 
position 



asymmetric 



x 



OH's in pi 
•yr positk 



ara 

on 



Finally the symmetrical compound can be obtained only 
from the meta, and it can yield only that tetra-substitu- 
tion product whose hydrogens are in the meta position: 

X X X 



xk^ x'^^x lx\^x 



in meta position 



symmetrical 



It will be noted that in the foregoing discussion only 
those compounds have received consideration which are 



228 OUTLINES OF ORGANIC CHEMISTRY 

produced by substituting the hydrogens of benzene by one 
other element. When the number of elements exceeds one, 
the number of possible isomers in the higher series is so 
much more complicated that we should not be repaid 
in following out all possibilities. Suffice it to say that 
here also facts contradicting the theory have not been 
established. 

When it is realized that the ring formula for benzene was 
suggested more than forty years ago, and that since that 
time the benzene derivatives have increased until they 
number tens of thousands, it must be admitted that there 
are few scientific hypotheses which are supported by such 
a multitude of facts. 

In practice the determination of the position occupied 
by a substituting group in a benzene ring {orientation 
as it is commonly called) consists in tracing out the 
genetic relations which connect that compound with cer- 
tain other well-known ones, for which the positions have 
been fixed by exhaustive special investigations: — with 
such, for example, as the bromine derivatives mentioned 
above. 

At this point a brief discussion of the two methods pro- 
posed on page 221 for disposing of the additional carbon 
valency would not be out of place. Against the formula 
containing alternate single and double bonds, two experi- 
mental objections can be raised. The double bond is 
usually considered as a sign of unsaturation, and as a sign 
of weakness, especially toward oxidizing agents. Now ben- 
zene is exceptionally stable toward oxidizing agents, and it 
acts like a saturated compound. Although benzene deriva- 
tives can be made to add halogens, and although several 
other addition-reactions can be effected, these are generally 
accomplished with very considerable difficulty. Substitu- 
tion usually takes place instead, 



BEXZEXE AXD ITS HOMOLOGUES 



229 



Another objection is found in the number of possible 
isomers. According to a strict interpretation of this formula, 
two ortho-substituted dibrombenzenes, for example, might 
be expected to exist. These would differ in the sense of 
the folio wing formulae: 



Br 






Br 



and 




X^ 



the bromine atoms being separated in one case by a single 
bond, in the other by a double one. Such isomers have 
not been observed with certainty. Kekule, who originally 
suggested this formula, afterward modified it by the state- 
ment that it should not be regarded as representing a rigid 
structure, but rather the end-stages of an oscillation be- 
tween the form:, 



and 



^y 



If a hypothesis of oscillation is to be accepted, most of 
the differences between the formula of Kekule and that of 
Baeyer disappear, for one can be regarded as representing 
the oscillation arrested in one point and the other in another. 
The latter formula has the advantage that in combining all 
the residual affinities of carbon in the center of the ring, it 
gives an explanation for the extraordinary stability of that 
complex. On the other hand it is true that most of the 
syntheses of benzene derivatives from aliphatic compounds 



230 



OUTLINES OF ORGANIC CHEMISTRY 



lead naturally to the Kekule formula. The whole question 
is, however, more of speculative than of practical interest, 
and the important reactions of the compounds involved 
can be satisfactorily interpreted with the aid of either 
formula. 

THE HOMOLOGUES OF BENZENE. 

When one or more hydrogens in a benzene ring are sub- 
stituted by alkyl radicles like methyl, ethyl, etc., there 
results a homologous series of hydrocarbons whose physical 
and chemical properties are analogous to those of benzene 
itself. Correct names for these compounds can be derived 
by prefixing to the word benzene the name or names of 
the substituting alkyl radicles. In this way such names as 
methylbenzene or isopropylbenzene are obtained. It so hap- 
pens, however, that several of these hydrocarbons have such 
technical or scientific importance that they have obtained 
special names of their own. Below will be found a list of 
names and formulae of those hydrocarbons of this series 
which are probably best worth keeping in mind: 




H,C 



CH, 




Toluene meJa-Xylene Mesitylene 

Toluene like benzene is found in coal-tar and shares with 
benzene itself a great technical importance as the source 
from which many useful substances may be prepared. It 
is a colorless oil lighter than water. It has an odor re- 
sembling that of benzene, and boils at 110°. 



BENZENE AND ITS HOMOLOGUES 231 

raeta-Xylene, the most common of the xylenes, is also 
found in considerable quantities in coal-tar, and has proper- 
ties very much like those mentioned. It boils at 139°. 

Mesitylene, or symmetrical trimethylbenzene, is a liquid 
boi ling~at^T64 °. It is chiefly interesting because of its for- 
mation from acetone when that substance is condensed by 
the action of sulphuric acid: 



CH 3 



CH 3 



CO I 

H-C C-H 



ILC 7 CH, / C % 



up I pn = ll ' +3H 2 0. 

±i 3 o +tu h 3 C-C C-CH 3 

CO CH 3 X C^ 

I I 

CH 3 H 

This is one of the best- known transitions from the aliphatic 
to the aromatic series. 

p-Cymene, or para-methylisopropylbenzene, is a con- 
stituent of several essential oils. It is mentioned here be- 
cause it is allied in constitution with some of the natural 
terpenes. There will be occasion to revert to this fact when 
these important substances are taken up. 

Many of the methods of preparation of the aromatic 
hydrocarbons are analogous to those employed for obtaining 
the hydrocarbons of the aliphatic series. If, for example, 
one of the aromatic acids or its calcium salt be heated with 
an excess of lime, carbon dioxide is removed by the latter 
and a hydrocarbon distills over: 

C 6 H 5 -COOH+CaO = CaC0 3 +C 6 H 6 . 

When an aromatic halogen compound like brombenzene 
is f reated with an alkyl halide in the presence of sodium, 



232 OUTLINES OF ORGANIC CHEMISTRY 

sodium bromide is formed and the two organic radicles enter 
into combination: 

C 8 H B Br + Na 3 + BrC 3 H 5 = 2 NaBr +C 6 H 5 -C 2 H 5 . 

This reaction is especially important as a means of orienta- 
tion, that is of fixing the position of an alkyl group in a 
benzene ring. Rearrangements are seldom observed and 
it can generally be assumed that the alkyl group takes that 
place in the ring originally occupied by the halogen. 

Another method for the preparation of the aromatic 
hydrocarbons should be mentioned which differs widely 
from any hitherto encountered. An alkyl chloride does not 
react with benzene when the two are mixed, but if a little 
anhydrous aluminium chloride be added, there is evolution 
of hydrochloric acid and a homologue of benzene is formed: 

C 2 H 5 C1 +C 6 H = HC1 +C 2 H 5 — C 6 H 5 . 

Ferric chloride and chromium chloride can sometimes be 
substituted for the aluminium chloride with good results. 
The mechanism of the reaction is not perfectly understood, 
though in some applications of it, well-characterized inter- 
mediate products containing aluminium have been isolated. 
The reaction is not always a pure catalysis, for in most cases 
these intermediate products do not regenerate aluminium 
chloride. An important condition for the success of the 
reaction is that the halide employed be aliphatic in character 
(see following section) and that the hydrogen which forms 
the other component of the hydrochloric acid evolved belong 
to a benzene ring. If these conditions are reversed, if, for 
example, hexane were treated with chlorbenzene, no re- 
action would result. The reaction is not of much use as a 
means of determining the constitution of the products, on 
account of frequent rearrangements and numerous side- 
reactions. It is, however, often extremely valuable for 
the laboratory preparation of many important compounds. 



BENZENE AND ITS HOMOLOGUES 233 

In discussing the chemical behavior of the aromatic hydro- 
carbons, a sharp line must be drawn between those atoms 
which belong to the benzene ring or nucleus, and those which 
form a part of the substituting alkyl groups. The latter 
are usually said to belong to a side-chain. The difference 
may be summed up concisely by saying that ring hydrogen 
is aromatic in character, while side-chain hydrogen is ali- 
phatic. This means that those hydrogen atoms which are 
in the ring react readily, for example, with nitric and sul- 
phuric acid, to form sulphonic acids and nitro-compounds 
(see reactions under benzene). The hydrogen of the side- 
chain, however, is more inert and resembles that of the 
hydrocarbons of the methane series. On the other hand, 
the side-chain is much more susceptible to the action of 
oxidizing agents, and so conspicuously is this the case that 
the following general rule holds good: When an aromatic ' 
hydrocarbon is subjected to the action of vigorous oxidizing 
agents, each side-chain which it contains is changed to a 
carboxyl group, and the latter occupies the same position 
as the original side-chain. This rule is of great value in 
determining the constitution of the aromatic hydrocarbons. 
A simple example will make this clear. It will be seen at a 
glance that the four compounds whose formulae are written 
below are isomers, and that it will therefore not be possible 
to distinguish between them by analysis: 



CH 2 -CH 3 CH 3 CH, CH, 

r^jCH 3 




L,Ii 3 LH 3 



CH q 



If they be oxidized, however, the resulting compounds must 
be the four following acids; 





234 OUTLINES OF ORGANIC CHEMISTRY 

COOH COOH COOH COOH 

O COOH o» 



and since the constitutions of all the carboxyl-substituted 
benzenes have been thoroughly worked out, those of the 
three hydrocarbons are at once fixed by the reaction. 

HALOGEN COMPOUNDS. 

The halogen compounds of the aromatic series again serve 
to illustrate the differences in chemical character between 
the benzene ring and the side-chains. When aromatic 
hydrocarbons are treated with chlorine or bromine in the 
sunlight and at a boiling temperature, substitution of the 
hydrogens in the side -c hain takes place. WnenThowever, 
the reaction takes place in the cold, and not in the direct 
sunlight, substitution is effected in the ring. For carrying 
out the latter reaction, catalytic agents are usually employed. 
Prominent among these is metallic iron. This is one of 
those cases in which the mechanism of the catalysis is well 
understood, and on that account it deserves a word of 
notice. The iron and bromine first react to form ferric 

bromide: 

Fe+Br 3 = FeBr 3 . 

The latter reacts with benzene, for example, to form brom- 
benzene and hydrobromic acid: 

C 6 H 6 + 2 FeBr 3 = 2 FeBr 2 +HBr +C 6 H 5 Br, 

and ferrous bromide. Finally the ferrous bromide again 
takes up an atom of bromine: 

FeBr 2 +Br = FeBr 3 , : 



BENZENE AND ITS HOMOLOGUES 235 

and the series of reactions is repeated. In cases of this sort 
the iron is said to act asa" carrier." The proof of the cor- 
rectness of the above interpretation lies in the fact that 
each of the three reactions will take place separately. The 
product of the particular reaction cited may serve as a type 
of the other products of this class. It is a colorless liquid 
insoluble in water. It has the specific gravity 1.517, and 
boils at 155°. Another name for this compound is phenyl 
bromide, and the name phenyl for the group C 6 H 5 is one 
which the student should" "fix carefully in mind. This 
radicle is fully as important as methyl or ethyl. When chlo- 
rine or bromine acts upon a hydrocarbon containing a single 
side-chain under the conditions just described, substitution 
still takes place in the ring; and from the theory it is clear 
that the formation of three isomeric products might be 
expected. Those which might be formed from toluene are 
indicated below: 

CH 3 CH 3 CH 3 

O Ob, O. 

Br 

As a matter of fact, it is the para and ortho compounds 
which predominate as products of the reaction. Facts of 
this sort are difficult to remember, but fortunately there is 
an empirical rule by the aid of which it is usually possible to 
predict the constitution of the resulting compound when a 
mono-substituted benzene derivative receives a second sub- 
stituent. The rule is that when the first substituent is one 
of the following five groups, viz.: — N0 2 , S0 3 H, COOH, CHO, 
and CN, the second substituent may be expected to assume 
the meta position to that already occupied. If it is some 
group other than these five ; substitution takes place in the 



236 OUTLINES OF ORGANIC CHEMISTRY 

para and ortho positions. It is generally true in this case 
that more para than ortho is formed. The five groups are 
not difficult to remember, for the first three suggest the 
important inorganic acids, nitric, sulphuric, and carbonic; 
while the aldehyde and nitrile groups are easily associated 
with carboxyl because they both easily go over into it, the 
first by oxidation and the second by saponification. It 
is not claimed that the rule is of universal application, but 
it covers a large number of cases, and indicates what may 
generally be expected. A few examples will serve to make 
clear the application of the rule. Under the influence of 
bromine, 

CH 3 CH 3 CH 3 

O viekis 0* and Q Br 



hv 



Br 




BENZENE AND ITS HOMOLOGUES 237 

Br Br 

and 
0, 



O yields on I 
nitration \X 




When toluene is treated with chlorine in the sunlight and 
at boiling temperature, no substitution takes place in the 
ring, but the hydrogens of the side-chain are successively 
replaced by chlorine. The products are benzyl chloride, 
C 6 H 5 CH 2 C1; benzal chloride, C 6 H 5 CHC1 2 ; and benzo trichlo- 
ride, C 6 H 5 CC1 3 . These compounds are liquids having an 
extremely irritating effect upon the mucous membrane of 
the throat and eyes. The student should take pains to fix 
in mind the word benzyl, the name of the radicle, C 6 H 5 CH 2 — . 
It is of common occurre'nce" 

The chemical properties of the aromatic halides differ 
according to whether the halogen atoms are situated in the 
ring or in the side-chain. It will be remembered that the 
halides of the aliphatic series are very reactive substances, 
which freely exchange the halogen atom for other groups 
or radicles. This reactivity of the aliphatic halogen extends 
to the aliphatic portion of the derivatives of benzene, — 
that is, to the side-chain. Halogen there situated shows 
the same reactivity which characterizes the aliphatic halides, 
and it is interesting to note that it is also available for use 
in the aluminium chloride synthesis (page 232). Benzyl 
chloride, for example, when treated with benzene in the 
presence of aluminium chloride, smoothly yields diphenyl 
methane: 

C 6 H 5 -CH 2 Cl + C e H = HC1 + C 6 H 5 -CH 2 -C G H 5 . 

With halogen which is situated in the ring, the case is 
quite different. Here the halogen is held so firmly that it 






238 OUTLINES OF ORGANIC CHEMISTRY 

can be replaced or removed only with extreme difficulty. 
An example of this is the fact that brombenzene yields no 
potassium bromide when treated with alcoholic potash, even 
after protracted boiling. In general the indifference of these 
aromatic halides is comparable to that of the hydrocarbons 
and ethers of the aliphatic series. 

THE SULPHONIC ACIDS. 

When benzene, or any of its homologues, are treated with 
concentrated, or better with fuming sulphuric acid, sul- 
phonic acids are formed: 

r ^ /° 

C 6 H 6+ H 2 S0 4 = H 2 + { >-S = . 

V — / x OH 

The accepted constitution of these compounds is expressed 
in the formula given. Evidence that they are not esters 
■of sulphurous acid is found in the fact that they cannot be 
saponified by the usual agents. Further, when their chlo- 
rides or anhydrides are subjected to the action of reducing 
agents the reaction proceeds as follows: 



o-<>.=o 



SH+HC1+2H 9 0. 



In the products of reduction, sulphur is directly connected 
to carbon, and the same holds true of the sulphonic acids, 
since no sulphur is split off in the operation. 

The sulphonic acids are strong acids very soluble in water. 
They usually crystallize with one or more molecules of that 
solvent, and are not volatile without decomposition. The 
simpler compounds of this type have little importance of 
their own, but great practical importance attaches to the 
class, because the presence of a sulpho-group makes a com- 
pound more soluble in water without, in general, much affect- 



BENZENE AND ITS HOMOLOGUES 239 

ing its other properties. This is of particular value in the 
manufacture of dyes. It is desirable that these should be 
soluble in water, and in consequence a large proportion of 
those upon the market are either sulphonic acids or salts 
of such acids. The coloring power of the dyes depends 
upon the presence of other groups. 

Suiphoniq^cids also possess importance as intermediate 
products in the preparation of phenols, but this reaction can 
well be postponed till that class of substances is taken up. 



CHAPTER XIV. 

AROMATIC NITROGEN COMPOUNDS. 

THE NITROCOMPOUNDS. 

When benzene or its homologues are treated with fuming 
nitric acid, or more commonly with a mixture of concen- 
rated nitric and sulphuric acids, the following reaction takes 
place: 



C 6 H 6 +HNO3 = H 2 + < >- N0 2 , 



> 



The products are called nitro-compounds. They are 
liquids or solids of strongly aromatic odor which on reduction 
in acid solution yield primary amines: 



( ^-NQ 2 +H 6 = 2H 2 0+ / y~ 



NH, 



This reaction is interesting from two widely differing 
points of view. Its technical importance lies in the fact, 
that the amines are valuable materials in the dyestuff 
industry, and they are, for the most part, prepared in this 
way. The reaction is theoretically important because it 
serves to fix the constitution of the nitro-compounds. For 
nitrobenzene, for example, the two following formulae might, 
at first sight, appear reasonable: 

( )~*C or 0"°" N=a 

_— — 240 



AROMATIC NITROGEN COMPOUNDS 241 

It is clear, however, that only the first is consistent with 
the formation of a primary amine upon reduction, for a 
compound of the second formula must either yield a product 
containing oxygen, or else the nitrogen would be completely 
split off as suggested in the following equation: 



/~Vo-N = 0+H 6 ^ \~~_J~ 



OH + NIL 



As intimated above, the nitro-compounds are chiefly 
important as intermediate products, rather than on account 
of any properties of their own. Consequently only nitro- 
benzene, the simplest member of the class, will be described 
here. It is an oil heavier than water, and is colorless when 
pure, though the technical product is always yellow on ac- 
count of an impurity which is difficult to remove. Nitro- 
benzene boils at 209° and is readily volatile with steam. It 
possesses an odor much like that of benzaldehyde, the 
characteristic ingredient of the oil of bitter almonds. In 
consequence it finds use as an adulterant and substitute for 
this more expensive material in confectionery and similar 
products. This is unfortunate, as nitrobenzene is quite 
poisonous. 

Nitrobenzene is prepared technically in enormous quanti- 
ties, and almost all of it is immediately reduced, in order to 
obtain the most important of the primary amines, aniline. 

THE AROMATIC AMINES. 

The primary amines of the aromatic series are prepared 
almost altogether by the reduction of the corresponding 
nitro-compounds. For laboratory purposes on the small 
scale, the reagents used are tin and concentrated hydro- 
chloric acid. In technical work the cheaper iron and sul- 
phuric acid are usually employed. The secondary and 



242 OUTLINES OP ORGANIC CHEMISTRY 

tertiary aromatic amines are generally obtained by processes 
of substitution in the primary compounds. As far as the 
methods used require description, they will be mentioned 
in connection with the individual products. The amines 
are oils or solids of a heavy odor which is sometimes desig- 
nated as " basic." They are generally volatile with steam, 
and, in chemical properties, show a certain analogy to the 
amines of the aliphatic series. It will be remembered that in 
the latter compounds the resemblance to ammonia was 
strongly marked. Those aromatic amines, however, in 
which nitrogen is connected directly to a benzene ring no 
longer possess the odor of ammonia; they are insoluble in 
water, and are decidedly weaker bases than either ammonia 
or its aliphatic derivatives. It is customary to account 
for this fact by the statement that the phenyl group is more 
negative in character than the alkyl radicles, though the 
exact significance of this expression might prove a little 
difficult to determine. Nevertheless, to say that a given 
radicle is " positive " or " negative " is a constantly re- 
curring expression in organic chemical discussion, and the 
student should early familiarize himself with the point of 
view involved. The present case is well adapted to serve 
as an example. 

It is generally true that the aliphatic amines are stronger 
bases than ammonia. Accordingly the alkyl radicles are 
said to be more positive or basic than hydrogen. Aniline 
on the other hand is a weaker base than ammonia, and the 
negative influence of the phenyl groups is still more clearly 
seen when more of the hydrogens of ammonia are substituted. 
Diphenylamine, 

hn( 

C 6 H 5 
is a much weaker base than aniline, — so much so that its 



AROMATIC NITROGEN COMPOUNDS 243 

salts are decomposed by dilution with water. Triphenyl- 
amine, 

/C 6 H 5 
N-C H 5 , 
C 6 H 5 

has ceased to be a base at all and is not even soluble in acids. 
Finally pure aromatic bases of the type suggested by the 
following formula do not exist: 

C 6 H 5 

C 6 H 5 

Inasmuch as radicles cannot be isolated either as such or 
in solution, it has not yet been possible to procure adequate 
numerical data by which the positive or negative character 
of a given group can be fixed quantitatively. This gives a 
certain vagueness to the whole underlying idea, and this 
vagueness is in no wise helped by the fact that when substi- 
tuted in certain compounds a given group sometimes exerts 
an influence upon the character of the product quite out of 
harmony with what is known of it elsewhere. The phenyl 
group, for example, is an important and apparently essential 
constituent of certain very strong bases. Despite such in- 
consistencies, the idea of positive and negative radicles is 
essentially helpful, but the student should understand its 
limitations. 

Another marked difference between the aliphatic and 
aromatic amines especially concerns the primary com- 
pounds. It will be recalled that the aliphatic representa- 
tives of this type react with nitrous acid in such a way that 
the amino-group is replaced by hydroxyl: 

C 3 H 5 *NH 2 ,HC1+HN0 2 = HC1 +H 2 + N 2 +C 2 H 5 OH. 



244 OUTLINES OF ORGANIC CHEMISTRY 

This result can also be obtained in the aromatic series, but 
here certain important intermediate products are formed 
which are extremely reactive: 

C 6 H 5 NH 2 , HCl + HNO a = 2 H 2 +C 6 H 5 N 2 C1. 

These are called diazonium salts, and the various transforma- 
tions of which they are capable are so interesting and impor- 
tant that they will be treated a little later as a separate topic. 

In addition to the differences already mentioned, the^aro- 
matic amines show the characteristic reactions belonging to 
the hydrogens of the benzene ring. They can, for example, 
be chlorinated, brominated, and sulphonated with even more 
readiness than the aromatic hydrocarbons themselves. Con- 
sidering the amines as benzene derivatives, it may be said 
that the amino-group has a tendency to make especially 
reactive that hydrogen which stands in the para position to 
itself, and some of this reactivity extends to the ortho 
position as well. Amines are also more susceptible to the 
action of oxidizing agents than are most benzene derivatives, 
and many of the reactions involved are very complicated. 
They will receive attention only where the importance of 
the products makes it necessary. 

Aniline, the simplest possible aromatic amine, is a com- 
pound of the highest technical importance, especially for 
the development of the dyestuff industry. So much is 
this the case that the term " aniline dyes " has come, in 
popular usage, to stand for all synthetic coloring matters de- 
rived from coal-tar. Aniline is prepared technically by the 
action of iron and hydrochloric acid upon nitrobenzene. 
An interesting detail of the process is the small amount of 
acid required. It so happens that when, at the start, a little 
ferrous chloride has been formed, this acts . catalytically in 
such a way that the reduction of the bulk of the nitrobenzene 
is effected by the metallic iron directly, so that only one- 



AROMATIC NITROGEN COMPOUNDS 245 

fortieth as much hydrochloric acid is required as would be 
calculated from the equation: 

C 6 H 5 N0 2 +6 HC1 +Fe 2 = 2 FeCl 3 +2 H 2 +C 6 H 5 NH 2 . 

Aniline is an oil heavier than water, and soluble in that me- 
dium only to the extent of about 3%. It is colorless when 
pure, but on standing acquires first a reddish and finally 
a very dark color, probably due to oxidation. Aniline 
boils at 184° and is readily volatile with steam. This 
property is frequently made use of in isolating it from a 
reaction mixture in which it has been set free. As a base, 
aniline forms salts by direct union with acids. These are 
crystalline compounds more or less soluble in water. The 
acid sulphate is soluble only with considerable difficulty. 
The salts all hydrolyze to a certain extent in aqueous solu- 
tion and react acid with the ordinary indicators. 

One of the most sensitive tests for aniline is a color re- 
action which it shows with hypochlorites. If a few drops 
of a solution of bleaching powder be added to an aqueous 
solution of aniline, a dark violet color appears on standing, 
even if the aniline solution is extremely dilute. 

Homologues of aniline are of three kinds. These may be 
thought of as derived from aniline, (1) by the substitution 
of alkyl radicles for hydrogen in the benzene ring, (2) by the 
substitution of alkyl radicles in the amino-group, (3) by 
the transfer of the amino-group to the side chain. 

Typical members of the first class are the three toluidines, 
ortho, meta, and para. Of these the ortho and para com- 
pounds possess technical importance. For their prepara- 
tion, the toluene from coal-tar is nitrated, and the mix- 
ture of ortho- and para-nitrotoluenes reduced without being 
separated. Finally, the mixed toluidines are distilled with 
a quantity of sulphuric acid insufficient to neutralize both. 
or^o-Toluidine then distills over, while the para compound 



246 OUTLINES OF ORGANIC CHEMISTRY 

remains behind as a sulphate. or^o-Toluidine is a liquid 
which boils at 197°, para-toluidine is a crystalline solid which 
melts at 45° and boils at 198°. The chemical properties 
of both are strictly analogous to those of aniline. 

Prominent members of the second group are the tech- 
nically important compounds, methylaniline and dimethyl- 
aniline : 

CH, / V m CH 3 



><• o< 



CH 3 



As the formulae indicate, one is a secondary and the other a 
tertiary amine. Since the hydrogens of ammonia are here 
substituted by both aliphatic and aromatic radicles, such 
bases are frequently referred to as " mixed." These com- 
pounds are commonly prepared by heating aniline with 
methyl alcohol and sulphuric acid. Both are liquids boiling 
at 192°, and are suggestive of aniline itself in their physical 
and chemical properties. They differ from that compound 
in not being primary amines. 

Of the third type of homologue, only one need be mentioned, 
benzylamine, 



O 



CH.-NH 



This compound is an isomer of the toluidines, but its amino- 
group is located in the side chain. This constitution is 
sufficiently established by several methods of preparation, of 
which only one, that from benzyl chloride and ammonia, 
need be mentioned here : 

C 6 H 5 -CH 2 C1 +2 NH 3 = NH 4 C1 +C 6 H 5 -CH 2 - NH 2 . 
As might be expected, this substance more closely resembles 
the aliphatic amines than do any of the bases previously 
described. It is a liquid boiling at 187°. It is soluble in 
water and is a strong base which even absorbs carbon dioxide 
from the atmosphere. 



X NH. 



AROMATIC NITROGEN COMPOUNDS 247 

Another aromatic amine should be mentioned in this con- 
nection, viz. diphenylamine: 

C 6 H 5 
C 6 H 5 

As its formula indicates, this is a pure aromatic secondary 
amine. It is of considerable technical importance in the 
manufacture of certain dyes and is prepared technically by 
heating aniline with its hydrochloride to a temperature 
of 140°: 

C 6 H 5 NH 2 +C 6 H 5 NH 2 .HC1 = xNH 4 Cl + ' 5 )NH. 

C 6 H 5 

Diphenylamine is a crystalline solid which melts at 54° and 
boils without decomposition at 310°. Its slight basicity 
has already been referred to. In addition to its technical 
importance, diphenylamine is a familiar reagent. The deep 
blue color which it gives with even minute traces of nitric 
acid is one of the most delicate tests for the presence of that 
substance. 

THE DIAZO-REACTION. 

Allusion has already been made to the fact that treatment 
of the primary aromatic amines with nitrous acid leads to 
the formation of diazonium salts. When it is desired to 
isolate the latter, it is usual to prepare the salts of the amines, 
dissolve these in alcohol, and add amyl nitrite and hydro- 
chloric acid to the solution. These react, yielding nitrous 
acid, which then acts upon the salt of the amine in the manner 
indicated by the following equation: 



V N -CI +HN0 2 = 2 H 2 + f "V. N-Cl. 
/ I \ f III 

H 3 N 



248 OUTLINES OF ORGANIC CHEMISTRY 

The product being insoluble in alcohol is precipitated di- 
rectly. The appropriateness of the graphic formula here 
given will be discussed a little later. The diazonium salts 
are usually highly colored substances (red or yellow), in- 
soluble in alcohol, but very soluble in water. Such solutions 
are neutral toward indicators, and contain the salts in a 
highly ionized condition. In this respect, these substances 
resemble the ammonium salts, and the name, diazonium, 
is intended to recall this resemblance, as well as the fact 
that the compounds contain two atoms of nitrogen to one 
benzene ring. The compound whose formula has just been 
given is called phenyldiazonium chloride, and this sufficiently 
illustrates the system of nomenclature in use. 

In the dry state, salts of this type are extremely explosive, 
and this property would render them unsafe to work with, 
were it not that most of their characteristic transformations 
can be effected in dilute aqueous solution. This makes it 
possible to obtain the final products without isolating the 
diazonium salts themselves at all. When this is desired, 
the method of preparation just outlined is not followed. 
Instead the amine is dissolved in dilute aqueous acid, and, 
while keeping the solution cold, the calculated quantity 
of a cold dilute solution of sodium nitrite is cautiously 
added: 

C 6 H 5 -NH 2 ,HC1+HN0 2 = 2 H 2 +C 6 H 5 .£f 2 CL 

The solution now contains the diazo-compound and is sus- 
ceptible of a great number of transformations, of which 
some of the most important will be briefly mentioned: 

(1) If the aqueous solution be simply heated to boiling, 
nitrogen escapes, hydrochloric acid is formed and hydroxyl 
takes the place in the benzene ring originally occupied by 
the amino-group: 

C 6 H 5 N 2 C1 + H 2 = HC1 + N 2 +C 6 H 5 OH. 



AROMATIC NITROGEN COMPOUNDS 249 

The product belongs to the class of compounds which will 
be studied later under the name of phenols. 

(2) If the solution be reduced by means of alkaline stan- 
nous chloride, the diazo-group is eliminated completely and, 
in the particular case cited, benzene is formed: 

C 6 H 5 N 2 C1 +H 2 = HC1 + N 2 +C 6 H 6 . 

This is a general reaction, and serves in scientific work to 
discover the hydrocarbon from which a given unknown 
amine is derived. 

(3) If the reduction be carried out in acid solution, the 
nitrogen is not evolved, and a hydrazine is formed: 

C 6 H 5 N 2 C1+H 4 = HCl + C fl H 5 -NH-NH 2 . 

Phenylhydrazine, w hose formula appears in the equation, 
is an important reagent for al dehydes and ketones. With 
such substances it reacts, in the sense of the following 
equation: 



C R H K -NH-NH 9 +0C / 



R' 

H 2 0+C 6 H 5 -NH-N = C; • 

>R' 

The products formed are called hydrazones. Some mention 
was made of them in connection with the sugars, in the study 
of which they have proved of especial value. 

(4) If a solution of a diazonium salt be treated with 
cuprous chloride, bromide, or cyanide, nitrogen is evolved, 
and chlorine, bromine, or cyanogen is substituted in the 
benzene ring: 

2 C 6 H 5 N 2 C1 +Cu 2 CN 2 = Cu 2 Cl 2 +2 N 2 +2 C 6 H 5 CN. 

The introduction of cyanogen is of particular importance 
because the products are nitriles of aromatic acids: 

C 6 H 5 CN+2H 2 = NH 3 +C 6 H 5 COOH. 



250 OUTLINES OF ORGANIC CHEMISTRY 

Hence the diazoreaction furnishes an indirect means of 
replacing the aminogroup by carboxyl. 

(5) By the addition of potassium iodide to a diazo-solu- 
tion, the nitrogen complex may be replaced by iodine with- 
out the use of copper salts: 

C 6 H 5 N 2 C1+KI - KC1+N 2 +C 6 H 5 I. 

This is perhaps the most convenient method for introducing 
iodine into a benzene ring. 

(6) Finally, there remains a reaction which leads to the 
formation of an extremely important group of dyes. If a 
diazonium salt be treated in a neutral or alkaline solution 
with a secondary or tertiary aromatic amine or with a phenol, 
a reaction takes place in the sense of the following equation: 

CH Q 



V N 2 C1 + / V- N 



CH, 



— / CH 3 

The acid component of the diazonium salt reacts with a 
ring hydrogen of the tertiary amine or phenol, and the re- 
maining radicles become united in the manner denoted in 
the formula. In the example given the tertiary amine has 
a hydrogen atom in the para position to the amino-group. 
When this is the case, it is that atom which reacts with 
the diazo-compound. When the para position is otherwise 
substituted, the reaction usually takes place with a hydrogen 
in ortho position. In any case, the product belongs to the 
class of substances called azo-dyes. The chief evidence 
for the constitution of these compounds is to be found in 
their behavior upon reduction. In this particular case, 
treatment with tin and hydrochloric acid would lead to the 
formation of aniline and p-aminodimethylaniline: 



AROMATIC NITROGEN COMPOUNDS 251 

CH 3 



X CH Q 



V- n = N— V V- N 

<^ ^-NH 2 +H 2 N -/ V N 



/CH 8 

N CH 3 ' 

These results show two things: first, that since the two 
nitrogens of the azo-group were separated by the reduction, 
one of them must have been connected with each benzene 
ring in the original dye. Secondly, the formation of para- 
aminodimethylaniline shows that the coupling of the di- 
methylaniline with the phenyl diazonium chloride took place 
in the para position. Both of these find expression in the 
formula given. 

CONSTITUTION OF THE DIAZONIUM SALTS. 

Since the dyes have the constitution just derived, it would 
at first seem natural to give the salts formulae like 



O 



N = N-C1, 



and as a matter of fact this was done until comparatively 
recently. Some of the reasons for the change of view are 
the following: It has already been pointed out that the 
aqueous solutions of the diazonium salts show similarity to 
those of the ammonium salts, and it has therefore seemed 
more rational to formulate these compounds with a penta- 
valent nitrogen. The formation of the azo-dyes need not 
be considered as an argument against this formula, for these 
dyes are usually formed in alkaline or at least neutral solu- 
tion, and it has been shown by a great mass of experimental 
evidence which need not be summed up here, that, under 
the influence of alkalies, the diazonium salts are changed to 
compounds whose constitution may be typified by the for- 
mula, C 6 H 5 — N = N — OK. These and not the diazonium 
salts are therefore to be looked upon as most closely 
related to the dyes. 



252 



OUTLINES OF ORGANIC CHEMISTRY 



THE AZO-DYES. 

Since the azo-dyes are the first as well as one of the most 
important groups of such substances which we shall have 
to consider, this is an appropriate time to ask what is to be 
understood by the word dye, and what chemical character 
is to be associated with such compounds. 

It is clear at the outset that not every colored substance 
is necessarily a dye. If a piece of wool be dipped in a 
solution of sodium chromate, it is colored brilliantly yellow, 
but a few minutes washing in running water will make it as 
white as before. A dye, then, must possess color and also 
a certain affinity to the fiber. It is generally recognized that 
these different properties depend upon the presence of certain 
specific groups in the dyestuff molecule. The following 
discussion will serve to give an idea of the kind of reasoning 
by which the functions of the different radicles are deter- 
mined. 

Benzene is a colorless substance, as are also most of its 
simpler derivatives, so that there is no occasion to regard 
the phenyl group as associated in any way with color. 
Azobenzene, however, 



V N = N-/ \ 



is dark red. It is therefore argued that th e co lor is due 
to_ the grouping — N = N — . Further substantiation of this 
view is found in the fact that any modification of this 
complex influences the color, thus hydrazobenzene 



V-NH-NH-/ 



is colorless. This azo-group then is called a chro?nophore 
or carrier of color. It is present in all the azo-dyes and 
gives its name to the class. Azobenzene itself, however, is 



AROMATIC NITROGEN COMPOUNDS 253 

not a dye, lacking affinity to the fiber. If an amino-gronp 
be introduced into it there is obtained the simplest possible 
azo-dye, commercially known as " aniline yellow": 



> X = N < 



-NH 3 . 



This differs from azobenzene only by the presence of the 
amino-group. Hence to the latter is ascribed the power of 
giving affinity to the fiber. Such a group is called an 
auxochromv or helper of the color. It usually exerts also 
a marked influence upon the shade. The more common 
auxochromes, in this as well as in other classes of dyes, are 
the hydroxy] group and the free or substituted amino-group, 
for example, 

/ CH S H 

OH, NH 2 , - N ' ' ~ N x > etc - 

CH 3 C 6 H 5 

It is not equally practicable to give a list of the common 
chromophores, for while there is general agreement that 
most dyes possess a chromophore, there is, in many cases, 
the widest difference of opinion as to exactly what the real 
chromophore is in a given case. The whole subject of the 
relation of color to chemical constitution is at the present 
time in a most unsettled condition, and the nature of chro- 
mophores, the functions of auxochromes, and the influence 
of salt formation are all subjects of much controversy. 
Fortunately there is less difference of opinion concerning 
the azo-dyes than almost any other group, and so this class 
is particularly well adapted for the exposition of the 
theory. 

In addition to the possession of color and affinity to the 
fiber, it is desirable for practical reasons that a dye should 
be soluble in water. Since the presence of a sulpho-group 
can usually be depended upon to give this property without 



254 OUTLINES OF ORGANIC CHEMISTRY 

appreciable influence upon the color, such groups are intro- 
duced into most dyes intended for technical use. 

The formula of the well-known indicator helianthin (whose 
sodium salt is also known as methyl orange), 



l-r/ \_N=N-< ^-N 



offers a convenient example for illustrating and reviewing 
the points just mentioned. For its preparation, sulphanilic 
acid (formed by the action of concentrated sulphuric acid 
upon aniline) is diazotized and coupled in alkaline solution 
with dimethylaniline. The product possesses the chromo- 

phore group — N = N — , the auxochrome — N , and 

X CH 3 
the sulpho-group — S0 3 H, which insures solubility in water. 
Its constitution is fixed by the fact that upon reduction the 
products are p-aminodimethylaniline and sulphanilic acid: 

vr( 3 +h 4 = 

PIT 

ss( 3 . 

X CIL 



- / ) ~ NH,+H,N- ^ y 



In the foregoing discussion, the question why the dye 
should adhere to the fiber at all has received no attention, 
nor is it possible to say much upon this subject at this time 
which is much better than a guess. Three theories at least 
have adherents and all are supported by more or less con- 
vincing experimental evidence: (1) the large molecules of 
the dye are enmeshed mechanically in the fiber, (2) the dye 
forms a solid solution in the fiber, (3) the dye forms a chemi- 
cal compound with the fiber. 

The truth probably is that all these influences are more 



AROMATIC NITROGEN COMPOUNDS 255 

or less at work in most practical cases. In the present state 
of the subject it would certainly be inappropriate to enter 
into discussion of their respective merits. One word may, 
perhaps, be ventured concerning the relation between the 
auxochrome groups and the chemical theory. Amino-groups 
are basic and aromatic hj^droxyls are weakly acid. Further, 
it will be recalled that silks and wools are essentially albumi- 
nous. Since compounds of the latter class probably have 
constitutions like the polypeptides, they contain both 
amino- and carboxyl-groups. This fits them for enter- 
ing into salt-like combinations with either acidic or basic 
dyes. 

It is also an interesting fact that while many dyes will 
impart their color to silks and wool, they cannot be dyed 
upon cotton without a mordant. Those which require a 
mordant are known as " adjective " dyes in distinction to 
those which dye directly and are called " substantive." The 
use of mordants in dyeing will receive more attention when 
we come to study the alizarines. 

In point of numbers the azo-dyes exceed all the others. 
The reason for this appears when it is realized that any 
primary amine may be diazotized and then coupled with 
any secondary or tertiary amine, or with a phenol. In con- 
sequence, the number of azo-dyes theoretically possible 
defies calculation. In practice the number is limited by 
the cost of material, the fastness of the color, and the de- 
sirability of the shade from an aesthetic point of view. In 
color, the simpler members of this class vary from yellow 
through orange and reddish brown to red. Several methods 
are known, however, by which it is possible to multiply 
almost indefinitely the number of azo-groups in the product, 
and in this way all colors, even blues and purples, can be 
obtained. How complicated are the structures of some of 
these dyes is well illustrated by the accompanying formula: 



256 OUTLINES OF ORGANIC CHEMISTRY 

HO ; CH 3 , 



ISTaOaS 




S0 3 Na 





SO.Na 



OH 



This represents the constitution of a dye known to the trade 
as Direct Heliotrope B. 

The determination of the constitution of such a compound 
is not so difficult a matter as the appearance of its formula 
would seem to indicate, for, in the first place, it usually can 
be predicted with a good deal of certainty from the nature 
of the materials coupled together in its preparation, and 
the order in which they were employed. These conclusions 
might be verified and extended by subjecting the product 
to the action of reducing agents. It might then be con- 
fidently expected that it would split in the manner indicated 
by the dotted lines in the formula, when the separation and 
identification of the amines found in the reaction mixture 
would give satisfactory evidence of the constitution of the 
original substance. 



4o 



m,k* 




fo Ait (««^ 



CHAPTER XV. 

AROMATIC OXYGEN COMPOUNDS 

THE PHENOLS. 

The most important method for the preparation of the 
phenols has already been mentioned. It consists in boiling 
the diazonium salts with water: 

C 6 H b N 2 Cl +H 2 = C 6 H 5 OH+ HC1 + N 2 . 

Another method which is sometimes useful is the fusion of 
the sulphonic acids with caustic alkali : 

C 6 H 5 -S0 3 H +3 KOH = K 2 S0 3 +2 H 2 +C 6 H 5 -OK. 

The formulae of these substances suggest a resemblance to 
the alcohols, and this is borne out 7 to a certain extent, by 
their chemical behavior. They show, for example, several 
of the familiar hydroxyl reactions, forming ethers, esters, 
and the like. Nevertheless, the negative character of the 
phenyl group makes itself felt in the increased acidic proper- 
ties of the phenols. They are weak acids, it is true, for the 
most part weaker than carbonic acid, but they dissolve 
readily in alkalies to form salts called phenolates. From 
sucBTsolutkmB- they can usually be precipitated by the action 
of gaseous carbon dioxide: 

C 6 H 5 OK+C0 2 +H 2 = KHC0 3 +C 6 H 6 OH, 

and this reaction can frequently be used to advantage for 
isolating and purifying them. 

Considered as benzene derivatives, the phenols share with 
the amines the increased reactivity of those hydrogens in 
the ortho and para positions to the hydroxyl group. Like 

257 



258 OUTLINES OP ORGANIC CHEMISTRY 

these compounds, they couple with diazonium salts to form 
azo-dyes : 



Vn 2 ci+ \__y- 

Vn= N— / A-OH 



A genetic relationship which has not hitherto been men- 
tioned also connects these two classes of compounds. When 
the phenols are treated with the addition product of zinc 
chloride and ammonia, amines are formed: 

C 6 H 5 OH+ NH 3 = H 2 +C 6 H 5 NH 2 . 
In some cases, this reaction is of importance for the prepara- 
tion of primary amines. 

V Phenol, par excellence, commonly called " carbolic acid, " 
has the formula, C 6 H 5 OH. It is the simplest member of 
the group and its properties are quite typical. It may be 
prepared by either of the general methods already mentioned. 
It occurs in considerable quantities in coal-tar, where it is 
accompanied by several homologues. These can all be re- 
moved from the tar by shaking with alkali. Phenol is a 
crystalline solid which melts at 42° and boils at 182°. It 
is volatile with steam. When freshly prepared, it is color- 
less, but on standing exposed to the light it rapidly assumes 
a reddish tint. Phenol itself is a violent poison and exerts 
a destructive influence upon the skin or mucous membrane, 
at the same time producing a kind of local paralysis. It 
finds extensive use as a germicide and most phenols exert 
more or less action of this kind. 

xr Picric Acid. When phenol is nitrated, three nitro groups 
are easily introduced. These distribute themselves sym- 
metrically, occupying the para and two ortho positions with 
reference to the hydro xyl group. Their influence is to 
increase the acidity of the compound. The product is 



Lrj»»~~t") i**^)- 



■i 



AROMATIC OXYGEN COMPOUNDS 259 

called picric acid. It is a } r ellow crystalline solid which 
melts at 122°. By careful heating, it may be sublimed with- 
out decomposition, a remarkable fact when it is realized 
that the military explosive " melinite " is made of this 
material. For vigorous explosive effects a suitable detonator 
must be employed. Picric acid is one of the first synthetic 
substances to be used as a dye. It colors woolen directly, 
but not cotton. If a mixed cotton and woolen fabric be 
dyed with picric acid and then washed out, the woolen fibers 
will become yellow, while the cotton will not be affected. 
By means of a magnifier it is not difficult to count the number 
of yellow fibers in a given field and so ascertain roughly the 
proportion of wool in the fabric. Picric acid is formed 
when nitric acid acts upon various albuminous substances 
such as skin, hair, etc. The familiar stains which nitric 
acid produces upon the hands are due to the formation of 
this substance. The fact that these are rendered more 
intense by washing with alkali, illustrates the fact that the 
salts of picric acid are more highly colored than the free acid. 
Like the latter, they are explosive. 

The Cresols. Of the homologues of phenol, the three 
cresols or methyl phenols occur in coal-tar. It is, however, 
rather difficult to separate them from this mixture, and the 
pure compounds are usually prepared synthetically. They 
closely resemble phenol in their properties. 

T he Polyatomic Phe nols. The diatomic phenols are 
crystalline solids which do not possess such irritating action 
upon the tissues as phenol and its lower homologues. The 
simplest ones are the dihydroxybenzenes, and all three are 
important: 0H 0H 0H 

F«—^ O CJoh O 

OH 

Pyrocatechol Resorcinol Hydroquinone 



260 OUTLINES OF ORGANIC CHEMISTRY 

They have special names which were applied before the 
benzene theory was worked out. The ortho compound is 
called pyrocatechol; the meta, resorcinol; and the para, 
hydroquinone. There will be occasion to speak of each 
more in detail later on. Hydroquinone is a reducing agent 
and finds extensive employment in photography as a de- 
veloper. As the student is probably aware, the process of 
development consists in the application of a mild reducing 
agent to silver bromide which has been exposed to light in 
a camera. Those portions of silver bromide which have 
received most light are then reduced more rapidly and 
completely to metallic silver than the others. In this way 
a " negative " image is obtained. 

Of the trihydroxybenzenes only the vicinal compound 
will be mentioned. This is called pyrogallol. As the name 
indicates, it is usually prepared by the distillation of gallic 
acid: 



HO OH 

OH 
OoH 



HoA y COOH = C0 3 + C j 

HO 3(ak fifi**f 

It is a light, crystalline solid very soluble in water. Its 
alkaline solutions rapidly absorb oxygen from the atmos- 
phere and this leads to its use in gas analysis for the deter- 
minations of free oxygen in gas mixtures. Pyrogallol is also 
much used as a developer. 

The Aromatic Alcohols. From the phenols must be 
sharply distinguished those benzene derivatives which have 
hydroxyl groups in the side-chain. These compounds do 
not possess the acidic properties of the phenols. They are 
neutral substances resembling in their chemical behavior 
the aliphatic alcohols. The compounds of this class are 
of little practical importance. Benzyl alcohol may be men- 
tioned as a type. The constitution of this substance is 



AROMATIC OXYGEN COMPOUNDS 261 

clear from its formation by the hydrolysis of benzyl 
chloride : 

C 6 H 5 - CH 2 . CI +H 2 = HC1 +C 6 H 5 • CH 2 . OH. 

It is a liquid which boils at 206°. It is soluble with difficulty 
in water. The oxidation of compounds of this type leads 
to the formation of aldehydes or ketones according to the 
position of the hydroxyl group, just as in the fatty series. 



THE AROMATIC ACIDS. 

The chief methods for the preparation of the aromatic 
acids are already familiar. They include (a) the oxidation 
of the aldehydes or alcohols, (b) the oxidation of aliphatic 
side chains, (c) the saponification of the nitriles. The 
aromatic acids are solids and strong acids, the degree of 
acidity often showing a marked dependence upon the other 
substituents which may be present in the benzene ring. 
They form the familiar acid derivatives, salts, chlorides, 
amides, anhydrides, esters, etc. In chemical behavior, these 
derivatives show no marked differences from their aliphatic 
prototypes, except in matters which do not depend upon the 
carboxyl group. 

Benzoic Acid. Benzoic acid is the simplest member of 
the class. It may be considered as a benzene in which one 
hydrogen has been replaced by the carboxyl group. It 
receives its name from gum benzoin in which it occurs. The 
commercial product is, however, almost entirely obtained 
by the oxidation of toluene : 



VcH 3 +0 3 = H 2 + \__V 



COOH 



Benzoic acid is a crystalline solid which sublimes on heat- 
ing. It possesses an extremely characteristic odor which is at 



*r 



262 OUTLINES OF ORGANIC CHEMISTRY 

once aromatic and suffocating. When benzoic acid is heated 
with an excess of lime, benzene is produced. This is entirely 
analogous to the formation of methane by heating sodium 
acetate with lime. As a benzene derivative, benzoic acid 
may be chlorinated, sulphonated, etc. 

This may be an appropriate time to mention a derivative 
of o rlfeo-sulphobenzoic acid . This is the imid, commonly 
known as " saccharin ": 




.qo 



O 

NH 
S0 2 * 

It is often prescribed in order to satisfy the craving for 
sweets experienced by sufferers from diabetes, who are 
not allowed sugar in their diet. The substance is 500 
times as sweet as cane sugar but has not the same physio- 
logical action as the latter, and, unlike it, is in no sense a 
food. 

X Salicylic Acid. Salicylic or or^o-hydroxybenzoic acid 
has obtained some importance in medicine as a remedy for 
rheumatism and also as an antiseptic. Its salts are not 
infrequently employed as food preservatives. The acid is 
best prepared by the action of carbon dioxide upon sodium 
phenolate under pressure : 

COONa 
ONa r^OH. 





This peculiar reaction, in which carbon dioxide seems to 
force itself between a hydrogen atom and the ring, is of 
quite general application for the preparation of compounds 
of this type. The methyl ester of salicylic acid occurs in oil 



AROMATIC OXYGEN COMPOUNDS 263 

of wintergreen, and imparts the characteristic taste and 
smell to that substance. 

The Phthalic Acids. There are three acids which may 
be thought of as derived from benzene by substituting two 
hydrogens in that compound by carboxyl groups. These 
are known as the phthalic acids. They have all been of 
great importance in the development of chemical theory, 
and in fixing the constitution of aromatic substances. Here 
attention will be called only to the ortho compound which 
has some particularly interesting derivatives. When the 
word phthalic acid is used alone it is always this compound 
which is understood. It is produced on the large scale 
by the oxidation of naphthalene, and from this method 
of preparation derives its name. The reaction itself will 
be more clearly understood after naphthalene itself has been 
studied. When phthalic acid is heated above its melting 
point, it loses water, forming an anhydride which sublimes 
in long, white needles : 

<;-COOH "*>♦ CO ' 

Thfs anhydride is manufactured technically in great quanti- 
ties, since it is usefulin the preparation of many important 
dyes, among them synthetic indigo. 

Mellitic Acid. When/ciiarcoal or graphite are oxidized 
by nitric acid or bv^ermanganates in alkaline solution, 
mellitic acid iH^ 5 .ied. It also occurs as an aluminium 
salt in a natura> / mirte«al known as " honey stone. " It can 
be prepared synthetic allytryothe oxidation of hexamethyl 
benzene, and this method of formation, as well as the fact 
that it yields benzene when heated with lime, fixes its con- 
stitution as benzene hexacarboxylic acid : 




264 OUTLINES OF ORGANIC CHEMISTRY 

CH 3 COOH 

CH 3 ^CH 3+9 HOOC^SCOOH 

CH 3 COOH 

COOH 

HOOcr^NcooH +6Ca0 = 6 p, 

HOOCk^COOH \^J . 

COOH 

The preparation of this substance from amorphous carbon 
is interesting as an indication that the molecule of the latter 
contains at least twelve carbon atoms, and that it contains 
the benzene nucleus. 



THE ALDEHYDES. 

The aldehydes of the aromatic series may be prepared by 
the oxidation of primary alcohols. More frequently they 
are formed by heating the calcium salts of the acids with 
calcium formate, 

C 6 H 5 COO v HCOO . .0 

^Ca+ ^Ca = 2CaC0 3 + 2C 6 H 5 -Cf > 

C 6 H 5 COO X HCOO / X H 

or by the saponification of those halides which have two 
halogen atoms united to a single carbon of the side chain: 

C 6 H 5 -CHC1 2 +H 2 = 2 HC1 +C 6 H 5 CHO. 

Not infrequently, also, aldehydes may be prepared by the 
cautious oxidation of certain hydrocarboJs. 

The chemical behavior of the aromatic aldehydes differs 
from that of the analogous aliphatic compounds in several 
minor particulars. These hardly affect, however, a general 
similarity. The aldehydes possess characteristic and for 
the most part agreeable odors. For this reason the CHO 



AROMATIC OXYGEN COMPOUNDS 265 

group is sometimes referred to as an " odorophore." Many 
of these substances occur in essential oils, and find use as 
perfumes or flavoring extracts. Benzaldehyde is found in 
bitter almonds, cinnamic aldehyde in cassia and cinnamon, 
vanillin in the vanilla bean: 

o r~ 



VcH-CH-CHO 
X H \ ' 

Benzaldehyde Cinnamic aldehyde 

OH 



CH 3 




CHO " 

Vanillin 

Benzaldehyde, the simplest member of the group, is techni- 
cally prepared by boiling benzal chloride with lime water: 

C 6 H 5 CHC1 2 +Ca(OH) 2 = CaCl 2 +H 2 +C 6 H 5 CHO . 

It finds extensive employment in the dyestuff industry. 
It is a colorless liquid boiling at 179° and possessing the 
odor characteristic of bitter almonds. It readily absorbs 
oxygen from the air, forming benzoic acid. The occurrence 
of benzaldehyde in the bitter almond is of interest. Here 
it exists in the form of a glucoside called amygdalin. In 
the ceils of the bitter almond there is also a ferment known 
as emulsin. When the almond is macerated with water, 
this ferment comes in contact with the amygdalin and, 
under its influence, the latter is lrydrolyzed, forming benz- 
aldehyde, glucose, and hydrocyanic acid. 

THE KETONES 

For the preparation of the aromatic ketones, three methods 
of preparation will be considered. The first is the familiar 
one consisting in the dry distillation of the calcium salts of 
the acids; 



266 OUTLINES OF ORGANIC CHEMISTRY 

C 6 H 5 -COO. C 6 H 

^Ca = CaC0 3 + ,CO. 

CeH.-COO 7 C 6 H/ 

The second method is not available in the aliphatic series. 
It is essentially an adaptation of the aluminium chloride 
synthesis whose application to the preparation of hydro- 
carbons has already been discussed. In preparing ketones, 
acid chlorides are treated with aromatic hydrocarbons in the 
presence of aluminium chloride: 






o 

Finally ketones may be prepared by the oxidation of certain 
hydrocarbons : 



/C 6 H 5 


/C 6 H 5 


CH 2 + 2 = 


= H 2 + C = 


C 6 H 5 


C 6 H 5 



Only one of the individual compounds need be mentioned. 
This is benzophenone whose formula appears in the above 
equations. It is a crystalline solid of characteristic, faintly 
aromatic odor. It melts at 46° and boils without decom- 
position at 307°. It shows the characteristic ketone re- 
actions and on reduction yields a secondary alcohol called 
benzhydrol : 



C 6 H 5 C 6 H 

1 ' / 

co +h 2 = c ; 

i i 

C 6 H 5 C 6 H, 



AROMATIC OXYGEN COMPOUNDS 267 

THE QUINONES. 

Allied to the ketones is an interesting class of substances 
called quinones. It is perhaps most convenient to begin 
the study of these substances with the description of a single 
representative. When hydroquinone is treated with certain 
oxidizing agents, such for example as ferric chloride or chromic 
acid, a product is formed which contains two hydrogens less 
than hydroquinone, and differs from it strikingly in many 
respects. This substance is para-benzoquinone, often called 
simply quinone. It can be most economically prepared by 
the oxidation of aniline, but the reaction is complicated and 
the steps are even now but imperfectly understood. 

While hydroquinone is colorless, odorless, and volatile 
with difficulty, quinone is bright yellow, has an odor sug- 
gestive of chlorine and sulphur dioxide, and sublimes with 
great readiness, being extremely volatile with steam and 
even with ether vapor. It blackens the skin and is a vigor- 
ous oxidizing agent, readily liberating iodine from solutions 
of the iodides. Gentle reducing reagents such as sulphurous 
acid change it back readily to hydroquinone. Quinone 
shows many of the properties of the ketones, but if it is to 
be formulated as such, it is obvious that certain far-reaching 
modifications in the benzene ring must be assumed at the 
same time. The consequences involved are perhaps made 
most easily intelligible when the centric formula of Baeyer 
is assumed for benzene. On this basis, the formulae of 
quinone and hydroquinone would be written as follows: 

OH O 

I II "^ 

h-c;i;c-h — > H-cr X c-H 

Son; ' ; , ( ' « ii Qui — x 



H-c; I ;c-H < — H-C C-H 

I II 

OH O 



268 OUTLINES OF ORGANIC CHEMISTRY 

The formula ascribed to quinone requires the presence of 
two carbonyl groups whose carbon atoms form an integral 
part of a benzene ring. This can only be arranged by making 
use of two of the central bonds. The consequence of this, 
however, must be to destroy the symmetry of the combina? 
tion, and the four remaining bonds no longer point to the 
center but go back to the periphery, forming two sets of 
ordinary double bonds. If now it be assumed, as the Baeyer 
formula tacitly does, that the aromatic character is due to 
the central grouping of the internal bonds, a substance of 
the formula given could hardly be expected to show the 
properties of an ordinary benzene derivative. Instead it 
would be apt to behave like an aliphatic compound with 
two double bonds. This is in large measure true of quinone. 
It not only differs from hydroquinone in all the properties 
already mentioned, but, when treated with halogens, it adds 
two or four atoms, whereas true benzene derivatives behave 
for the most part as saturated compounds, and form addition 
products only with considerable difficulty. 

The formula just discussed has an importance w T hich far 
transcends that of the single compound just described. 
There are a great many colored substances, among them 
many important dyes, in which a similar " quinoid " arrange- 
ment of a benzene ring is generally assumed. Almost all 
such substances stand in close relationship to some other 
compound which is colorless and which contains two atoms 
of hydrogen more than the colored one. They stand, in 
short, to the latter in the same relationship as quinone to 
hydroquinone. Such a colorless substance is frequently called 
a leuko-compound (Greek, Acvkos, white). 

The quinoid structure has to be referred to so frequently 
that it is convenient to have some abbreviation for it in our 



formulae. That usually adopted is < V= . On this 



>■ 



AROMATIC OXYGEN COMPOUNDS 



269 




basis benzoquinone itself would be written O 

It has been recently discovered that if pyrocatechol be 
shaken with silver oxide in perfectly dry benzene solution 
an entirely analogous or^o-benzoquinone is formed: 



OH 



O 



OH 



+ Ag 2 = Ag 3 +H 2 




Resorcinol when subjected to similar treatment does not 
}deld a quinone, nor are other compounds having a meta- 
quinoid constitution known with certainty. An argument 
against the existence of such compounds (which, however, 
cannot be considered conclusive) is found in the somewhat 
grotesque arrangement of the carbon bonds which such a 
structure seems to demand : 



H- 



H- 



:~c/\ 



o 

II 

h-c ;o-h 



C N C-H H-<T "C-H 

(L J>o H-CA .6=0 



i 
H 



V 

H 




CHAPTER XVI. 

SOME IMPORTANT DYES. 

THE TRIPHENYLMETHANE DYES. 

It is now possible to examine briefly a few of the im- 
portant groups of dyes in which a quinoid chromophore is 
generally accepted. 

In the early days of the coal-tar-dye industry, it was found 
that when crude aniline oil was oxidized with arsenic acid, 
a base was formed whose salts imparted to cloth a deep red 
color. These salts were brought on the market under the 
name of " fuchsine " or " magenta " and soon had a large 
sale. To the base was given the name of rosaniline. Its 
constitution was then unknown, and any satisfactory ex- 
planation of its formation was for a long time wanting. It 
was soon learned, however, that the crude aniline oil was 
essentially a mixture of aniline with ortho- and para-tolui- 
dines. Later investigations revealed the fact that no one 
of these three compounds when oxidized alone gave any 
rosaniline, whereas a molecular mixture of the three yielded 
it in large quantities. It was also found that a similar 
base (pararosaniline) could be formed by oxidizing, in the 
same way, a mixture of one molecule para-toluidine and 
two molecules of aniline. The constitution of pararosani- 
line proved a little easier to fix than that of rosaniline itself, 
and its study furnished the key to the structure of the latter. 
When pararosaniline (C 19 H 19 ON 3 ) is reduced, it yields a 
substance free from oxygen which contains three amino- 
groups. By the diazo-reaction, it is possible to replace 
these by hydrogen (page 249). The product is triphenyl- 

270 



SOME IMPORTANT DYES 271 

methane. From this point, the student will find no diffi- 
culty in forming a clear idea of the constitution of these 
substances by following the steps of the following synthesis : 
When chloroform and benzene react in the presence of 
aluminium chloride, triphenylmethane is formed in accord- 
ance with the following equation: 

HCC1 3 +3 C 6 H 6 = 3 HC1 + HC -C B H, . 

C 6 H 5 

Nitration of this compound introduces three nitro-groups 
in positions para to the methane carbon atom : 




+ 3HNO, = 3H,0+H-( 




On reduction, the triamino-compound referred to above is 
formed. It is tri-para-triamino-triphenylmethane and is com- 
monly known as paraleukaniline : 




G 



NR 



HC -\ /-NO,+ 18 H = 6H 2 0+HC 



~ \ / -NH 2 

\nh 2 




On oxidation, this yields pararosaniline or tri-para-triamino- 
triphenyl-carbinol : 



272 OUTLINES OF ORGANIC CHEMISTRY 



NIL 





NIL 



-/" "\-NH 3 +0 - HO-C- ^ V 



NH, 



The salt formed by treating this base (which is colorless) with 
one molecule of acid constitutes the dye parafuchsine: 




HO 



O 

C-/^ ^-NH 2 + HC1 = H 2 Q + C-< ^ V 



NH 2 



NH,. 




NH 

/ \ 

H Cll 



The formation of pararosaniline by the oxidation of aniline 
and p-toluidine is now sufficiently clear. The methyl group 
of the latter base must furnish the methane carbon atom for 
the final product: 



H 

CH 




/ ) -NH, 

,/" ~VnH 2 +0 3 = 2R,0+HO-C- ^ ^ ~ 

+ 

/~~~Vnh 2 



NH, 




SOME IMPORTANT DYES 273 

The constitution of rosaniline and its formation by the 
oxidation of aniline, para-toluidine and or^o-toluidine are 
consequently to be expressed by the following equation: 
CH 3 



> 



NH 2 



CEL-< >- NIL + 3 =2H 2 + HO - C 



NIL 



O 




At this point, the student may wish to inquire why the 
complicated quinoid formula written above is assigned to 
the salts of pararosaniline and analogous compounds instead 
of the following apparently simpler one : 




Cl-C-< VNH 



> 
> 



> 



NIL 



This has been the subject of a long and vigorous contro- 
versy, and it cannot be claimed that the last word has been 
said upon the subject. The consensus of opinion at the 
present time undoubtedly favors the quinoid formula. 
For this only one reason will be suggested here. The bright 
color of fuchsine certainly seems to call for a different con- 
stitution from that of the corresponding carbinol. This is 



274 



OUTLINES OP ORGANIC CHEMISTRY 



colorless, and for it the constitution given is established by 
the fact that by means of the diazo-reaction, it readily goes 
over into triphenylcarbinol : 

HO-C-C.H, . 
C 6 H 5 

Fuchsine itself is a crystalline solid of semimetallic luster 
and green reflex. In its technical preparation, it has been 
found possible in recent years to substitute nitrobenzene 
for the poisonous arsenic acid as an oxidizing agent. 

There are many important dyes allied to the fuchsines. 
Substitution of various radicles for hydrogen in the amino- 
groups leads to the formation of products whose color is 
more nearly blue. Elimination of one amino-group gives a 
green product. A few formulae representing important dyes 
of this type follow: 

CH 3 




Crystal violet Aniline blue Malachite green 

If rosaniline derivatives be treated with nitrous acid and 
the resulting diazo-compounds boiled with water, sub- 
stances are produced which are known as aurins and rosolic 
acids. The analogy between these and the dyes just de- 



SOME IMPORTANT DYES 



275 



scribed is well brought out by the fact that they can be 
prepared by oxidizing phenol along with the cresols. The 
graphic formulae given below make these relationships 
sufficiently clear: 




OH 



> 




Rosolic acid 



THE PHTHALEINS. 

Another interesting group of colored compounds which 
are related to triphenylmethane can be prepared by the 
action of phthalic anhydride upon phenols. When these 
substances are heated together in the presence of some 
condensing agent, one of the carbonyl oxygens of the an- 
hydride unites with the hydrogens of two phenol molecules 
to form water, and the remaining radicles are united. In 
the phenols that hydrogen atom usually reacts which stands 
in the para position to the hydroxyl group. These relations 
can be illustrated in the simplest case by the following 
equation: 




CO 
\ 



Q+ 2 



/ 
CO 




HO 



= H„0 + 




OH 



4#JU^ 



276 



OUTLINES OF ORGANIC CHEMISTRY 



The product of this reaction is phenolphthalein whose 
use as an indicator is already familiar. It is a colorless 
substance which dissolves in alkalies to form a deep red salt 
containing two atoms' of the alkali metal. To this there is 
generally ascribed the quinoid constitution: 

KO ' 





C 



^ OK 

Phenolphthalein is not itself a dye, but there are several 
important dyes which belong to the same class of compounds. 
If, for example, resorcinol be used instead of phenol, an 
analogous condensation occurs. In this case, however, an 
additional molecule of water is formed from two of the 
phenolic hydroxyl groups as indicated in the equation below: 





HO 



2H,0 + 



aV°o oH 

CO 

The product forms salts of the formula 




OH 



,Q 



K °aD-° 




c 



CO 



OK 



SOME IMPORTANT DYES 277 

The solutions of these salts fluoresce with great brilliancy 
and this has given the name of fluorescein to the original 
condensation product. The fluorescence is so intense that 
it is noticeable in extreme dilution, and this substance has 
been used for tracing the currents of subterranean water 
courses. The sodium salt of fluorescein is brought on the 
market under the name of uranin. 

Fluorescein itself is now little used as a dye. A substitu- 
tion product, however, tetrabromfluorescein, better known 
as eosin, finds use in a number of ways, particularly for the 
dyeing of silk. 

INDIGO. 

This important blue coloring matter has been an article 
of commerce from the earliest times. Until recently its 
principal source has been the plant Indigofera tinctoria, 
which grows chiefly in India. In the sap of this plant there 
exists a glucoside consisting of a reduction product of indigo 
coupled with d-glucose. When the plant is macerated with 
water and exposed to the air, hydrolysis takes place followed 
by oxidation and indigo blue is formed. The crude com- 
mercial product contains several coloring matters of different 
tints. The principal one, indigotin, is a dark blue powder 
insoluble in water, alcohol, dilute acids, and alkalies. On 
careful heating it sublimes, forming beautiful prisms of 
metallic luster. The vapor of indigo is sufficiently stable 
to permit the determination of its molecular weight. 

For dyeing purposes, it is customary to reduce indigo 
blue by such reducing agents as grape sugar or the hydro- 
sulphites. The product is a colorless compound called 
indigo white. It contains two hydrogen atoms more than 
indigotin. It is soluble in alkalies, and when cloth is dipped 
in such a solution and exposed to the air, oxidation takes 
place and indigo becomes fixed upon the fiber. The eon- 



278 OUTLINES OF ORGANIC CHEMISTRY 

stitution of indigo was the subject of much study by some 
of the foremost investigators for many years, and several 
methods have been proposed for its synthetic preparation 
on the large scale. In recent years these have been so 
successful that the synthetic indigo has to a very large ex- 
tent replaced the natural product in the markets of the world. 
No attempt will be made here to give even a fragmentary 
review of these interesting investigations, nor will any rigid 
proof for the constitution of indigotin itself be presented. 
Instead, one of the more recent commercially successful 
syntheses will be briefly outlined. From this the constitu- 
tion of the product will be sufficiently apparent. 

When phthalic anhydride is treated with ammonia gas 
phthalimid is formed : 

CO ^XX) 

O + NH 3 = H 2 0+ f T ?TH 

This substance may be regarded as an internal anhydride 
of the compound, 

COOH 



CO.NH 2 



Now just as acetamide when treated with bromine and 
caustic potash goes over into methyl amine (page 118), 
so this substance under the influence of chlorine and caustic 
alkali loses a carbonyl group and yields or^/io-aminobenzoic 
acid — commonly called anthranilic acid: 





a 



COOH 
NH, 



SOME IMPORTANT DYES 279 

When the latter is treated with chloracetic acid, hydro- 
chloric acid is eliminated, and phenylglycine-ortfio-carboxylic 
acid is formed in accordance with the following equation : 

aCOOH /^COOH 

+ CteH 2 COCH=HCl+ 1 
NHH) \/^NH-CH 2 -COOH. 

When this substance is fused with alkali, carbon dioxide 
and water are split off, and a compound called indoxyl is 
formed: 

aCOOH 
y CH 2 COOH+2KOH = 



C xx 



,OH 



K 2 C0 3 +2H 2 + [ ^CH . 

This substance is closely related to indigo, and readily goes 
over into it by the most gentle oxidation, — even by contact 
with the air: 



/ OH 
")CH+0 2 



a 



NH 

Indoxyl 



... CO x /CO 



H 2 0+[ C = C J! 



Indigo 




CHAPTER XVII. 

NAPHTHALENE AND ANTHRACENE. THE COAL-TAR INDUSTRY. 

NAPHTHALENE. 

One of the most important hydrocarbons in the coal-tar 
distillate is naphthalene. This is a colorless, crystalline 
solid which melts at 79° and boils at 218°. It possesses a 
fatty luster and feel, it can be readily sublimed, and is 
volatile with steam. Naphthalene has the empirical formula 
C 10 H g , and a study of its constitution has led to the conviction 
that it consists essentially of two benzene rings which have 
two carbon atoms in common. This may find expression 
in either of the two formulae given below : 

H H 



I I 



H H 

I I 

H-C( I )C( l)C-H 

h-c' i ^c; I ^C-H 
x c / x c' 

I I 

H H 

Disregarding these minor differences, the formula is usually 
abbreviated to 





// 


C x/ 


C xx 




H- 


-C 

1 


C 

II 


C- 

1 


-H 


H- 


-C 


c 


c- 


-H 




^ 


c /x c' 

1 1 








1 
H 


1 

H 






in which the two hexagons have practically the same sig- 
nificance as that in the familiar symbol for benzene. 

280 



NAPHTHALENE AND ANTHRACENE 281 

The presence of one benzene ring in naphthalene is experi- 
mentally established by the ease and smoothness with which 
it yields phthalic acid on oxidation: 

^Y€OOH 
X^AcOOH 




O a = H 2 0+2C0 2 + 





For the existence of two such nuclei, the following interest- 
ing proof is usually presented. 

The nitration of naphthalene leads to the formation of a 
mono-nitro-compound which on oxidation yields the nitro- 
phthalic acid whose formula is given in the scheme below : 

N0 2 N0 2 

Hooc-r^^i 

HOOC-k^. 

This establishes the presence of one benzene ring, and the 
position of the nitro-group. The latter, however, is not 
essential for the argument. The same nitronaphthalene 
when reduced yields an amine which, on the basis of all 
known analogous cases, must have the amino-group in the 
same position as the nitro-group in the compound from 
which it was derived. This compound when oxidized does 
not yield an aminophthalic acid but phthalic acid itself: 
NO. NH 2 

COOH 






-COOH. 

The disappearance of the amino-group is evidence that the 
benzene ring which contained it has been destroyed by 
oxidation, while a second one must have existed in the 
original naphthalene, otherwise no phthalic acid could have 
been formed. 
The constitution of naphthalene just derived is supported 



282 OUTLINES OF ORGANIC CHEMISTRY 

by several syntheses and by the number of substitution 
products. Even a superficial examination of the formula, 

a a 

a a 

will suffice to show that all the hydrogen atoms cannot be 
equivalent. The four marked a will however be mutu- 
ally equivalent, and the same is true of the four marked /?. 
As a matter of fact, two series of monosubstitution products 
are known, and they are regularly distinguished as alpha- 
and 6eto-compounds. In individual cases the constitution 
is determined in a manner analogous to that employed in 
the case of the nitro-compound just cited. The compound 
is oxidized, and constitution of the resulting substituted 
phthalic acid determined. A more careful study of the 
naphthalene formula will reveal the fact that ten di-sub- 
stitution products are possible according to the theory. 
As a matter of fact ten dichlornaphthalenes are known, 
and it has been found possible to assign to each a constitu- 
tional formula. 

Naphthalene is essentially aromatic in chemical behavior. 
Its derivatives are in general analogous to those of benzene. 
Few of them have enough individual importance to detain 
us long. The phenols of this series, known as naphthols, 
and the amines, (naphthyl amines) as well as several other 
derivatives, are manufactured on a large scale chiefly for 
use as components of azo-dyes. The consideration of these 
various applications would, however, teach little that was 
new in principle. 

Naphthalene itself is sometimes employed as a cheap 
substitute for camphor as a protection for clothing against 
moths. Probably more naphthalene is oxidized for the 
preparation of phthalic anhydride than is used for any 



NAPHTHALENE AND ANTHRACENE 283 

other single purpose. This is really the first step in the 
indigo synthesis, and until recently it was usually carried 
out by the action of chromic acid. Were it necessary, 
however, to use this oxidizing agent on the large scale, the 
cost of production of phthalic anhydride would have been 
prohibitive for the economical manufacture of indigo. 
Fortunately it was discovered that the oxidation could be 
carried out smoothly and successfully by means of highly 
concentrated sulphuric acid if mercury salts were added as 
catalytic agents. 

ANTHRACENE. 

Another of the higher boiling constituents of coal-tar is 
anthracene. This is a crystalline solid which melts at 
213° and boils at 351°. When pure it is colorless, though 
the commercial product has a marked yellow shade. The 
perfectly pure substance shows a fine blue fluorescence. 

Having fixed the formula for naphthalene, that of an- 
thracene requires no prolonged discussion. Anthracene is 
believed to have three benzene rings connected in a similar 
manner to those in naphthalene. This may be expressed 
by formulae like the following : 



H H H 

I I I 



H H 

I I 



h-c c c c-h h-c; i ;c( i )c( i / C - H 

I II I I or 1/ ( v ( ) (l 

h-c c c c-h c-HVc;rc,i,c-H 
^c /x c^ x c^ c c c 



I I I 

H H H 



I I I 

H H H 



k t^t^p 




a 



284 OUTLINES OF ORGANIC CHEMISTRY 

Here it will readily be seen that three kinds of mono-sub- 
stitution products must be possible according as hydrogen 
atoms in the alpha-, beta-, or gamma-positions are replaced. 
This corresponds to the number actually existing. It is 
worthy of note that the hydrogens in the aamma-position 
are especially reactive. When anthracene is treated with 
bromine, for example, these two hydrogens are readily sub- 
stituted. When anthracene is treated with oxidizing agents, 
it is again the gamma-hydrogens which are acted upon: 

H O 





+ 3 = H 2 + 
H 6 

The product is called anthraquinone. It is a yellow, crys- 
talline substance which melts at 285° and boils at 382°. 
It may be considered as the mother substance of an impor- 
tant group of dyes called the alizarins. The most impor- 
tant of these is that found in the madder root. This plant, 
Rubia tinctorum, was long cultivated in France on a very 
large scale for the production of this dye. In the course 
of a chemical investigation of the latter, it was found that 
when distilled over zinc dust, it yielded anthracene. This 
gave the key to its constitution which, on further study, 
was found to be that of a dihydroxyanthraquinone. Soon 
after, it was found possible to synthesize it from anthracene. 
For that purpose, the latter is first oxidized to anthraquinone 
and that substance sulphonated. The product is a mono- 
sulphonic acid of the formula indicated below. When this 
is fused with caustic potash, the sulpho-group is replaced 
by hydroxyl, and, oxidation taking place at the same time, 
alizarin is formed: 



NAPHTHALENE AND ANTHRACENE 285 

coy-cOD-cQo^r 
— cCo« ■ 

^^ X CCK OH 

This method of preparation soon proved so much more 
economical than the production of the dye from madder, 
that the latter product was driven from the market, and the 
land which had been used for its cultivation again became 
available for the production of other crops. This achieve- 
ment has with justice been looked upon as one of the 
greatest industrial triumphs of Organic Chemistry. With 
it, of course, must now rank the production of synthetic 
indigo. 

Alizarin proper, the dyestuff whose preparation has just 
been described, sublimes in orange-red needles which melt 
at 290°. A less pure product is the yellowish alizarin paste, 
— the form in which the dye is usually applied. Most of 
the dyes heretofore considered were capable of dyeing at 
least wool and silk directly. With the alizarins the use 
of a mordant is necessary, and the color imparted to the 
fiber depends upon the nature of the mordant. 

If alizarin be dissolved in alkali, and to this solution there 
be added the salts of various metals, precipitates are thrown 
down which have different colors according to the metal 
employed; thus aluminium salts yield a red precipitate, iron 
a violet black, chromium a violet brown. These precipitates 
may be regarded as alizarin salts. They are commonly called 
" lakes," and find use as pigments. 

This makes clear the action of metallic salts as mordants. 
In practice, easily hydrolyzed salts, such as the acetates of 



286 OUTLINES OF ORGANIC CHEMISTRY 

aluminium, chromium, or iron, are usually employed. The 
cloth to be dyed is impregnated with these, and then boiled 
with alizarine paste, when the resulting precipitates are fixed 
in the fibers of the fabric. In calico printing the various 
portions of the design are frequently printed upon the cloth 
in different mordants, and then the colors brought out by 
a single dye. 

There is quite a large group of dyes to which the class- 
designation of alizarins is applied. This consists of anthra- 
quinone derivatives containing at least two hydroxyl groups 
and their various substitution products. The different com- 
pounds would not repay detailed consideration here. 



PHENANTHRENE. 

Isomeric with anthracene is the hydrocarbon phenanthrene. 
It also is found in coal tar, but has as yet no such wide 
application as anthracene or naphthalene. It is a color- 
less solid which melts at 99° and boils at 340°. The follow- 
ing formula represents its accepted constitution: 




The only point of general interest which now attaches to 
this substance is the fact that the opium bases, morphine, 
codeine, and thebaine are to be numbered among its deriva- 
tives. Since the constitutions of these important alkaloids 
have not yet been fixed with certainty, no good purpose 
would be served by suggesting possible formulae. 



NAPHTHALENE AND ANTHRACENE 287 



THE COAL-TAR INDUSTRY. 

Soft coal seems to have been distilled in comparatively 
early times for the preparation of coke. In the latter part 
of the seventeenth century, Johann Joachim Becher took out 
a patent for the preparation of tar by this method. He 
recommended the use of this material as a substitute for 
wood-tar in the treatment of cordage and for similar purposes. 
He also noted that inflammable vapors were given off in 
the process, and pointed out that these could be made use 
of for smelting, as they produced "a flame ten feet long." 

Little further advance seems to have been made until 
coal came to be distilled for the manufacture of illuminating 
gas. This was first done in England on a small scale by 
William Murdoch in 1792, but gas was first used generally 
for the illumination of cities about 1813. From this time 
on, the gas-making industry progressed rapidly, and the 
question of what to do with the by-products, ammonia and 
tar, became a serious technical problem. The latter was 
regarded as a special nuisance, and was for a time burned 
under the retorts as fuel. Later, partial distillation was 
effected, the light distillate being sold for use as a solvent — 
for india-rubber and other materials — while the residue 
found some employment as a preservative for timber. 

A new outlook was given to the industry by the discovery 
that the light oils contained benzene. This observation 
was made by A. W. Hofmann in 1845. Benzene itself had 
been discovered by Faraday twenty years earlier. 

The first aniline dye, mauve, was brought upon the market 
by Sir William Perkin, a student of Hofmann, in 1856. 
The introduction of fuchsine followed in 1859. From this 
time the use of coal-tar for the preparation of dyes increased 
rapidly. New impetus was given to it in 1868 by the 
discovery that alizarin could be obtained commercially from 



288 OUTLINES OF ORGANIC CHEMISTRY 

anthracene. This gave an increased value to the anthra- 
cene oil. Meantime the researches of Griess on the diazo- 
reaction (1858-1866) made possible the production of the 
great multitude of azo-dyes and so found use for a large 
quantity of naphthalene. The employment of naphthalene 
for the production of indigo dates from about 1894. 

Although the preparation of dyes has been the chief 
object in the distillation of coal-tar, the latter has served 
incidentally as the source of hundreds of other products 
of the most various qualities. Only explosives, perfumes 
and medicines need be mentioned here. 

The chief constituents of the tar are the hydrocarbons, 
benzene, toluene, xylene, naphthalene, and anthracene, 
together with several phenols, as well as pyridine and allied 
bases. It is needless to add that this is by no means a 
complete list. 

It would be impracticable to attempt to give an account 
of the manner in which coal-tar is treated technically for 
the production of these substances, as the methods of treat- 
ment vary widely in different establishments as well as 
under varying commercial conditions. In general it may be 
stated that the refining process consists in fractional dis- 
tillation alternated with treatment by chemical reagents. 
Of the latter, those chiefly used in treating the cruder portions 
of the tar are, first, dilute caustic soda for separating the 
phenols and other acidic materials from the hydrocarbons; 
second, dilute acid for removing pyridine and other bases; 
third, concentrated sulphuric acid, which attacks unsatu- 
rated compounds, thiophene derivatives, and miscellaneous 
impurities. In making the first distillation, the following 
temperature limits are commonly observed. 

Below 150°. — Light oil. This makes up from 3 to 5 % of 
the tar and is the source of the simple benzene derivatives. 

150°-210°. — Middle oil, 6 to 10 %. 



NAPHTHALENE AND ANTHRACENE 289 

210°-270°. — Heavy oil, 8 to 10 %. These two portions 
contain much naphthalene. 

270°-400°. — Anthracene oil. From this product the an- 
thracene is removed by chilling and consequent crystalliza- 
tion. The mother liquor is known as "dead oil," and serves 
for the preservation of timber. 

In the retorts there still remains a quantity of pitch 
amounting to rather more than 50 % of the original tar. 
This is used for such purposes as the preparation of stove- 
pipe varnish, asphalting, and the manufacture of waterproof 
roofing materials. 

The yields of purified products obtained from the original 
tar amount roughly to : — 

Benzene and toluene 1.0 — 1.5 % 

Phenol 0.5% 

Anthracene 0.25—0.45 % 

Naphthalene 6.0—10.0% 



CHAPTER XVIII. 

HETEROCYCLIC AND ALLOCYCLIC COMPOUNDS. 

HETEROCYCLIC AROMATIC COMPOUNDS. 

The aromatic substances hitherto studied may all be 
regarded as derivatives of benzene. There exist, however, 
many compounds whose aromatic character is undoubted, 
which nevertheless are not derivatives of benzene, and 
indeed possess other elements besides carbon in the nucleus. 
All are cyclic compounds: — that is, the constitutional for- 
mula of each contains a closed ring of some sort, but this 
is not to be regarded as the essential source of the aromatic 
properties. It will be seen later on that there are many 
cyclic compounds which are not aromatic. Those which 
are, however, show a certain curious similarity in structure. 
For each of them it is possible to write two formulae which 
stand to each other in the same relation as the Kekule and 
Baeyer formulae for benzene. A few examples will illus- 



trate this: 








HC-CH 

II II 


HC CH 

or | > / | 

HC CH 
\ / 




7 


HC-CH HC CH 

ii ii or i y/ 1 


HC CH 

\ / 






HC CH HC /X CH 
\ / \ / 

N N 
H H 




Furan 




Pyrrole j \ 

H H 


HC-CH 

II II 


HC CH 

or | ^ ( | 


HC 

II 


C C 
x ^CH HC(l)CH 

i or i ; ; i 

v y CH HC'l.CH 

x n' x n 7 


HC CH 
\ / 

S 


HC 7 X CH 
\ / 

S 


HC 


Thiophene 




Pyridine 



290 



HETEROCYCLIC AND ALLOCYCLIC COMPOUNDS 291 
H H H H 

c c c c 

HC^ X C 7 ^CH HC'l^c'l^CH 

i ii i or i ; ; " ; ; i 

HC V C\ /CH HCT i^CT |,CH 

H H 

Quinoline 

Compounds like the above which contain other elements 
besides carbon as components of the ring are commonly 
classed as heterocyclic. Two or three of them deserve at 
least passing notice. 

Thiophene occurs in small quantities associated with 
benzene in coal-tar. It remained undiscovered, however, 
for many years on account of the fact that not only thiophene 
itself but also most of its derivatives so closely resemble 
the corresponding derivatives of benzene that separation or 
distinction was hardly practicable. How remarkable is the 
resemblance may be suggested by the following table which 
compares the boiling points of several benzene derivatives 
with those of the corresponding compounds of thiophene. 

Boiling Pt. Boiling Pt. 



Benzene, 


80° 


Thiophene, 


84 


p-Dimethylbenzene, 


138° 


D imethy 1th iophene , 


135 ( 


Isop ropyl benzene, 


153° 


Isopropylthiophene, 


154 c 


Diphenylmethane, 


261° 


Dithienylmethane, 


267< 


Chlor benzene, 


132° 


a-Chlorthiophene, 


130' 


p-Dichlorbenzene, 


172° 


Dichlorthiophene, 


170 c 



Tetrabrombenzene, 324° Tetrabromthiophene, 326° 

Such a parallelism is remarkable evidence that the prop- 
erties of a chemical compound depend upon something else 
besides the identity of the elements which compose it. 

Pyridine. This substance, whose formula is given above, 
occurs in small quantities in coal-tar, but its chief source 
is the oil obtained by the distillation of bones. It is a 



i 



292 OUTLINES OF ORGANIC CHEMISTRY 

colorless liquid miscible in all proportions with water, as 
well as with most organic solvents. It has a peculiar, 
heavy, disgusting odor, and a depressing influence upon the 
nervous system. It boils at 115°. The constitution of 
pyridine is apparent from the following synthesis: There 
is an aliphatic compound, pentamethylenediamine, 

H 2 N - CH 2 - CH 2 - CH 2 - CH 2 - CH 2 - NH 2 , 

commonly called cadaverine on account of its occurrence in 
decaying corpses. When the hydrochloride of this substance 
is distilled, a molecule of ammonium chloride is formed and 
a cyclic compound called piperidine is produced. The latter 
substance derives its name from the fact that it occurs in 
pepper. On oxidation it yields pyridine: 



y CH 2 






y CH 2 


CH 2 CH 2 






CH 2 X CH 2 


! I 


= 


NH 4 C1 + 


1 1 +HC1 


CH 2 CH 2 

1 1 






CH 2 CH 2 


HC1.NH 2 NH 2 


HC1 




NH 


H 2 






H(y) 


C 






C 


/ \ 






/ ^ 


H 2 C CH 2 






HC CH (/3) 


1 1 


+0 3 


= 3H 2 + 


II 1 


H 2 C CH 2 






HC CH(a) 


\ / 






\ # 


N 






N 


H 









The constitution thus derived is confirmed by the num- 
ber of substitution products. There are, for example, three 
series of mono-substitution products according to the posi- 
tion which the substituent assumes relative to the ring nitro- 
gen. As indicated in the formula above, these positions 



HETEROCYCLIC AND ALLOCYCLIC COMPOUNDS 293 

are designated alpha-, beta-, and gamma-. The formula of 
pyridine is commonly abbreviated as follows: 




Quinoline like pyridine occurs in coal tar and in bone oil. 
It is a liquid boiling at 239°, and chemically it stands in the 
same relation to pyridine that naphthalene does to benzene. 
As a single illustration may be mentioned the fact that upon 
oxidation quinoline yields pyridinedicarboxylic acid. This 
is entirely analogous to the formation of phthalic acid by 
the oxidation of naphthalene: 




HOOC 



n 



+ 9 =2CO 2 + H 2 O+ H00C ,j 



/ 



THE ALKALOIDS. 

Pyridine and quinoline have been mentioned here because 
they may be looked upon as the mother substances of several 
of the important alkaloids; such, for example, as coniine, 
atropine, nicotine, and quinine. Though much study has 
been devoted to compounds of this class, only a few have 
been synthesized, and while the general character of most 
of them is quite well understood, there is still some disagree- 
ment with regard to minor details of structure. A word 
may not be out of place here concerning the meaning of the 
term " alkaloid." In practice, substances of the most 
diverse chemical constitution are included under this desig- 
nation. As the name indicates, they are all of a basic 
character. Other ideas commonly associated with the term 
include an animal or vegetable origin and the possession 
of marked physiological action. It has just been stated that 



294 OUTLINES OF ORGANIC CHEMISTRY 

many of these substances are associated chemically with 
pyridine and quinoline. Morphine and codeine, however, 
are derivatives of phenanthrene, caffeine is closely associated 
with uric acid, and cadaverine is a simple aliphatic diamine; 
yet all are commonly spoken of as alkaloids, and these illus- 
trations serve to indicate the ill-defined character of the 
term. No attempt will be made here to treat in detail 
the chemical properties of these substances. For these the 
student must be referred to special treatises. 

THE ALLOCYCLIC COMPOUNDS. 

The above designation is now commonly applied to the 
compounds which contain a closed ring of carbon atoms, 
and yet are not aromatic in character. The simplest of 
these is trimethylene : 

CH 2 | 
"^CH 2 . 

Without writing the formulae of all possible rings of this type, 
it is sufficient to state that all the cyclic polymethylenes 
up to nonomethylene (CH 2 ) 9 are known, and some of these 
have a great number of homologues and other derivatives, 
so that the total number of substances included in this 
branch of Organic Chemistry is already very large. Only 
those substances of this class will be alluded to here whose 
formulae contain at least one ring of six carbon atoms. 
It is clear that such compounds may be regarded as reduc- 
tion products of benzene derivatives, and, as a matter of 
fact, many of them can in practice be obtained in this 
manner. They are frequently referred to as hydroaromatic 
compounds. 
A case of this kind which has been studied with exceptional 



HETEROCYCLIC AND ALLOCYCLIC COMPOUNDS 295 

thoroughness is that of para-phthalic, or, as it is more 
commonly called, terephthalic acid : 

COOH 







I 
COOH 

This substance adds hydrogen with far greater ease than 
does benzene itself, and at the first step in the reduction 
a marked difference in chemical properties is noticeable 
between the products ' and the parent substance. Disre- 
garding possibilities of stereoisomerism, it will be observed 
that four dihydroterephthalic acids are possible, in accord- 
ance with the following formulae: 



COOH 

I 



• <\ 



H 2 C 
H,C X 



C 
I 
COOH 



/ 



CH H 2 C 

I I 

.CH HC 



COOH 

I 

CH 

c 

I 

COOH 



COOH 

I 



><\ 



H 2 C 



HC X /CH, 

CH 
I 
COOH 



COOH 
I .H 



X 



CH HC 



HC 



CH 
H 
N/ CH 

COOH. 



All of these substances are known and none of them are 
aromatic in character. The double bonds now show the 
properties usually associated with this type of structure in 
the aliphatic series. The compounds add halogen and are 
readily susceptible to the action of reducing agents, while 
oxidation frequently results in rupture of the ring at the 
point occupied by the double bond. The products of 
oxidation thus furnish the most important means of fixing 



296 OUTLINES OF ORGANIC CHEMISTRY 

the constitution of such substances. Those hydroaromatic 
compounds which occur in nature are, for the most part, 
allied to the terpenes. A strict interpretation of the latter 
word restricts its application to certain important hydro- 
carbons of the general formula, C 10 H 16 , which are hydro- 
aromatic in character. Many of them are more or less 
closely allied to cymene (page 231). These substances 
occur in the sap of conifera and in many essential oils. 
They usually possess agreeable, refreshing odors. Their 
constitution and mutual genetic relationships have been the 
objects of thorough investigations for the past twenty years, 
and though, at one time, this was considered one of the ill- 
developed divisions of the science, it is now one of the most 
fruitful fields of investigation. The study offers some 
exceptional difficulties, as the products are particularly 
liable to molecular rearrangement and to polymerization. 
New material is all the time being contributed, and some 
of the constitutional formulae which were once considered 
definitely established have recently been again called in 
question. 

A list containing a few names and formulae follows: — 

CH 3 CH 3 

I I 

,<\ ,°< 

H 2 C CH H 2 C CH 

II II 

H 2 C CH 2 H 2 C CH 2 

\ / \ / 

CH C 

I II 

C C 

//\ / \ 

CH 2 CH 3 ^H 3 CH 3 

Limonene Terpinolene 



HETEROCYCLIC AND ALLOCYCLIC COMPOUNDS 297 



CH< 
C 



ff 2 cr 

|CH 3 - 



CHj 

i 

c 



CH HC CH 3 ;CH 



C-CR 



H 2 C 



> 



CH H 9 C 



CH r 



C 
H 

Camphene 



^C 

I 
H 

Pinene 



CH 5 



One compound, pinene, deserves more than passing notice, 
since it is the chief constituent of American oil of turpentine. 
This product is obtained by distilling the sap of conifera 
with steam. It is a colorless liquid of characteristic odor 
boiling at 155°. It finds its principal use as a component 
of paints, in which it acts as a carrier of oxygen (page 146). 
Chemically it has served as a starting point in the commercial 
production of synthetic camphor. 

Closely allied with the hydrocarbons just alluded to are 
certain alcohols and ketones which are familiar substances. 
One example is menthol, 

CH, 



CH 
H C CH, 



I .H 



H 2 C 



/ 



CH 



OH 



CH 
CH a CH, 



the chief and characteristic constituent of oil of peppermint. 



298 



OUTLINES OF ORGANIC CHEMISTRY 



/ 



It is a crystalline solid melting at 42° and boiling at 
212°. Its characteristic odor and cooling taste are well 
known. 

Camphor. The natural product is a gum obtained from 
certain trees growing mostly in Japan. It is purified by 
distillation with steam. It melts at 175° and boils at 204°. 
Camphor is used extensively for combating the ravages of 
moths and similar pests.** Perhaps even larger quantities 
of it are used in the manufacture of celluloid (page 179). 
One of the results of the recent war between Russia and Japan 
was an increase in the price of camphor. This. gave new 
impetus to the attempt to prepare the compound syntheti- 
cally on a commercial scale. These efforts met with con- 
siderable success, and there is at the present time a good 
deal of the latter product upon the market. One of the 
methods which have been proposed for the purpose is the 
following. Pinene is first treated with hydrochloric acid. 
This results in the addition of one molecule of the latter. 
The product is next treated with alcoholic potash, which 
removes a molecule of hydrochloric acid. This is, however, 
split off in such a way that not pinene, but an isomeric 
hydrocarbon, camphene, is produced. To the latter is 
usually ascribed the formula given in the equations below. 
Camphene readily yields camphor on oxidation : 



Pinene 






CH 3 

6 



CH 3 

i 

c^ 



CH 3 CH 
C-CH,, 



H 2 C 
+ HC1 
CH 2 H 2 C 



.= |CH 3 - 



CHC1 



C-CIT 



CH S 



C 

i 
H 



cr 

i 

H 



HETEROCYCLIC AND ALLOCYCLIC COMPOUNDS 299 



CH, 

i v 



pk-O-CH 
H 2 C^J 



'CHC1 



H*C 



+KOH=KCl+H 2 + 
CH 2 H 2 C 





H 

Camphor 

The product is optically inactive, whereas natural camphor 
rotates the plane of polarized light to the right. Its optical 
activity can be easily accounted for in the usual way. It will 
be noticed that the formula given shows the presence of two 
asymmetric carbon atoms. 

INDIA-RUBBER. 

An important substance whose chemical constitution has 
been much in doubt is india-rubber or caoutchouc. This is 
obtained by drying the sap of certain trees grown chiefly 
in countries near the equator. Its elasticity and amorphous 
character are well known. It dissolves readily in several 
organic solvents, but the solutions are colloidal. The re- 
sults of analysis correspond to the formula, C 10 H 16 , but the 
true formula must be some large multiple of this, as there 
is every reason to think that the substance is a high polymer. 



300 OUTLINES OF ORGANIC CHEMISTRY 

India-rubber has the curious property of uniting directly with 
sulphur, and this union — known technically as vulcanization 
— adapts the rubber to its various technical uses, the hard- 
ness of the product being roughly proportional to the amount 
of sulphur chemically combined. In addition to this " sul- 
phur of vulcanization," most commercial rubbers also con- 
tain a good deal of sulphur which is not chemically combined, 
as well as numerous other substances added for one purpose 
or another. Sometimes these additions serve a useful pur- 
pose in fitting the rubber for its use in certain articles, and 
sometimes they are only added for purposes of adulteration. 
Their presence often makes the complete analysis of rubber 
articles a very complicated matter. 

On account of its percentage composition and also because 
some substances allied to the terpenes are formed when 
rubber is destructively distilled, it had until recently been 
assumed that caoutchouc was itself a polymerized terpene, 
and that it probably contained a ring of six carbon atoms. 
Recent investigations have gone to show, however, that it is 
more probably the polymerization product of a compound 
containing a ring of eight carbon atoms. 

The evidence upon which this conclusion is based is ex- 
tremely interesting. A wide study of the action of ozone 
upon unsaturated compounds has revealed the fact that 
most substances containing a double bond react with this 
reagent in the manner indicated below: 



R ^ \ 

\ CH CH 

II +o 3 = 



/ 3 



Three atoms of oxygen attach themselves to each double 
bond. 



HETEROCYCLIC AND ALLOCYCLIC COMPOUNDS 301 

These ozonides, when treated with water, usually react 
vigorously to form aldehydes as follows : 



R 



X C R-CHO 

|)0 3 + H 2 = + +H 2 2 . 
C R'-CHO 

R'' 

Now when india-rubber is treated with ozone in a dry chloro- 
form solution, such an ozonide is formed quantitatively, six 
oxygens being added to each ten atoms of carbon. This 
ozonide readily decomposes into levulinic acid and the 
corresponding aldehyde, CH 3 -CO-CH 2 -CH 2 -COOH and 
CH 3 — CO — CH 2 — CH 2 — CHO, substances of well-known con- 
stitution. This result makes probable for the ozonide the 
constitution, 

CH 3 

I 
0-CH 2 -CH 2 -CH 

°»(| | X 

HC-CH 2 -CH 2 -C / " 

I 
CH 3 

and for the original hydrocarbon that expressed by the 
formula, 

CH 3 

I 

C-CH 2 -CH 2 -CH 
I! II 

HC — CH 2 — CH 2 — C 
I 
CH 3 

An indirect substantiation of this view of the constitution of 



302 OUTLINES OF ORGANIC CHEMISTRY 

india-rubber may be found in the fact that a recent attempt 
to prepare a compound containing a ring of eight carbon 
atoms with two double bonds yielded a product which poly- 
merized with almost explosive violence. 

Gutta-percha is obtained from sources similar to those of 
india-rubber, and is doubtless allied to the latter in chem- 
ical composition. It contains oxygen. 



CHAPTER XIX. 

THE STRUCTURE THEORY. 

In the foregoing pages, chemical phenomena have been 
discussed from the point of view of the structure theory. 
This assumes that the properties of chemical compounds 
depend upon two factors : — the nature and proportions 
of the constituent elements, and the arrangement of the 
atoms of the latter within the molecules of the compounds. 
This arrangement is itself determined by a fixed or slightly 
variable saturation capacity for each element. It is further 
assumed that from the synthesis of a compound and its 
chemical behavior, it is possible to determine this structural 
arrangement. 

The student can hardly have progressed thus far in the 
study of the subject without having asked himself more than 
once whether — however logical the various constitutional 
proofs might appear — such a mechanical conception of the 
nature of matter is in any case justifiable; and whether it is 
possible that minute particles of matter can exist with such 
complicated structures as, for example, that suggested on 
page 198. 

It is believed that in a book of this kind such questions 
should receive frank discussion, but it has seemed better to 
place this at the end, in order that the student might approach 
it with some knowledge of the theory and with some ability 
to think in its terms. As a general principle, too, it is 
always advisable that a sympathetic insight into a subject 
should precede a critical examination of it. 

At the outset it must be pointed out that the fundamental 

303 



304 OUTLINES OF ORGANIC CHEMISTRY 

conceptions with which the theory under discussion deals — 
atoms, molecules, and valencies — are all hypothesis and 
not fact. This is a point which cannot be emphasized too 
strongly, since the young student — and unfortunately the 
more venerable investigator as well — is too often apt to 
disregard the gulf which separates the two. 

From the point of view of science, a fact is a natural 
phenomenon observed by the senses either directly or by 
means of instruments, such observation being then cor- 
rected for all sources of error known to be present in the 
media employed, including the sense organs themselves. 
The truth and validity of such a fact are obviously not 
absolute, since it cannot be certain, in a given case, that all 
sources of error are known or have been properly corrected; 
nevertheless it represents the maximum of truth concerning 
a given phenomenon which is obtainable by the senses. 
A hypothesis stands upon an entirely different footing. It 
is a statement of something inaccessible to direct observa- 
tion which, if it were a fact, would serve to coordinate and 
" explain" a number of other facts. It is hardly admissible 
to say that a given hypothesis is "true," for in that case 
it would be a fact and no hypothesis. On the other hand, 
a hypothesis is obviously false if there exist any perfectly 
well-established fact which contradicts it. In such a case, 
the hypothesis must be given up or modified to fit the fact. 
Such modifications have frequently resulted in the great 
strengthening of theories. As a rule, however, the contin- 
ued necessity of making subordinate hypotheses to keep an 
original one afloat must be regarded as a sign of weakness. 

To account for the stability of the earth in space, certain 
of the ancients asserted that it rested upon the back of an 
elephant. The difficulties caused by the elephant and his 
burden soon exceeded those of the original fact, and a hypo- 
thetical tortoise had to be introduced for him to stand upon. 



THE STRUCTURE THEORY 305 

This only transferred the difficulty to the tortoise, and so 
a score of other hypothetical beasts had to be invented. 
This is an example of an especially crude and useless hypothe- 
sis, whose falsity no one has found it worth while to demon- 
strate. 

On the other hand, the assumption that that form of energy 
which, acting upon the human retina, produces the impres- 
sion of light, consists essentially of vibrations in an impon- 
derable frictionless medium called the " luminiferous ether," 
■ — this assumption has served to satisfactorily coordinate 
and explain practically all the complicated phenomena of 
optics. The ether itself, however, remains as hypothetical 
a material as ever. 

In the truth or falsity of a hypothesis, the scientist does 
not — or rather should not — have too great an interest. 
The question which should concern him is that of its utility. 
A hypothesis is useful if it coordinates facts otherwise iso- 
lated, and if it offers a stimulus for the discovery of new 
facts. A good hypothesis thus helps the teacher by making 
a subject easier to demonstrate, the student by relieving the 
memory of the load of many isolated details, and the inves- 
tigator by suggesting experiments which test the validity of 
the hypothesis itself. 

Having stated the advantages of a good hypothesis, what 
are the disadvantages? Like the advantages, these lie in 
the nature of the human mind. We acquire a personal 
interest in the truth of those hypotheses in whose terms we 
are accustomed to think, and a kind of blindness for those 
facts which lie beyond its limitations. It has frequently 
occurred that important facts, necessary and valuable for 
the progress of science, have been for long periods brushed 
aside and discredited because they failed to accord with 
dominant hypotheses, and the healthy progress of human 
knowledge has been much retarded in this way. Further- 



306 OUTLINES OF ORGANIC CHEMISTRY 

more it is in the nature of every hypothesis to gradually 
wear out. Sooner or later a time comes when all attempts 
at patching fail, and the theory must be put aside and 
replaced by a more suitable generalization. There then 
frequently arises a long and often bitter controversy between 
the supporters of the old and those of the new. Whether 
such controversies are on the whole helpful to science or 
the reverse is a moot point. They often prove no mean 
stimulus to investigation, and bring out valuable facts. 
On the other hand, doubt may well be expressed whether the 
search for arguments in a desperate attempt to support 
one side of a passionate controversy produces the best 
frame of mind in which an investigator can approach the 
study of the truth. For these reasons many scientists 
believe that hypotheses have done more harm than good, 
and that it would be well to eliminate them altogether from 
the sciences. Instead there should only be permitted such 
generalizations from the facts as contain terms capable of 
being directly measured. These should preferably be put 
in mathematical form. 

Turning back to Organic Chemistry as we know it, there 
remain two questions to be asked: — (1) Is the valence or 
structure theory a good hypothesis? (2) Is all hypothesis 
so objectionable that to banish it from Organic Chemistry 
would be for the good of that science? 

There can be no doubt that the structure theory is a good 
hypothesis. It has coordinated quantities of apparently 
unrelated facts in a manner which has certainly not been 
excelled by any scientific generalization. It has brought 
these into a system. It is constantly giving the stimulus 
to new and profitable researches on practical as well as 
scientific lines, and it has again and again enabled chemists 
not only to imitate the products of nature, but to predict 
with surprising accuracy the properties of compounds 



THE STRUCTURE THEORY 307 

"when as yet there was none of them." Into these advan- 
tages of the theory, students must have derived some 
insight from the foregoing pages. In an elementary work 
of this kind, these have perhaps been made more prominent 
than the weak points. The fact should not be glossed over 
that weak points exist. In certain cases, there seem to be 
more isomers than the theory can very conveniently account 
for. There are substances whose present formulae seem very 
inadequate expressions of their chemical behavior. There 
are numerous chemical reactions for which the current 
explanations seem particularly lame and forced. Still 
throughout the history of the science such apparent excep- 
tions have always existed, and in the majority of cases 
further experimentation has finally turned them into brilliant 
confirmations of the theory. There is every reason to hope 
that the present difficulties may be overcome in a similar 
manner. 

For those who would tolerate in the science no hypothesis 
however good, the case may perhaps be fairly stated as 
follows: — The properties of a chemical compound depend 
upon two factors. One of these is its elementary com- 
position and the other its energy content. With these two 
non-hypothetical quantities as a basis, it should be possible 
to formulate expressions which should give all the informa- 
tion now furnished by our graphic formulae, and not burden 
our minds with a quantity of hypothetical material which 
must sooner or later be sacrificed. As a matter of fact, 
no such mathematical formulae as those suggested have ever 
been set up, nor has any adequate hint been offered by the 
opponents of the valence theory as to how this should be 
done. In the absence of such suggestions, it may be con- 
ceded that such formulae might give valuable quantitative 
information, yet it is difficult to see how they could ever 
provide those valuable hints as to the qualitative behavior 



308 OUTLINES OF ORGANIC CHEMISTRY 

of substances which constitute so important a part of what 
can be learned from a graphic formula. 

While the organic chemist will hardly be induced to for- 
sake a hypothesis which has so wonderfully justified itself 
by its results, certain profitable lessons can be derived from 
the discussion. One of these is the undesirability of using 
hypotheses when non-hypothetical generalizations are equally 
serviceable and available. Organic chemists are perhaps 
too prone to forget that graphic formulae are a means and 
not an end. They represent not a system of molecular 
architecture, but an epitome of chemical relationships and 
behavior. 

In conclusion the student is advised to use hypotheses 
and not to be abused by them; to distinguish in his study, 
and to keep carefully separate in his mind, that which is 
fact and that which is hypothesis; and finally to maintain 
so impartial a mental attitude that when the time comes, 
he will be ready to replace the old forms by new and more 
appropriate symbols. 



INDEX 



Acetaldehyde, 61, 147. 

Acetamide, 102. 

Acetates, 88. 

Acetic acid, 88. 

Acetic acid, constitution, 83. 

Acetic anhydride, 93. 

Acetone, 113. 

Acetone, condensation to mesity- 
lene, 231. 

Acetyl, 92. 

Acetyl chloride, 91. 

Acetylene, 129. 

Acetylene, condensation to benzene, 
219. 

Acid amides, 101, 120. 

Acid anl^drides, 93. 

Acid chlorides, 91. 

Acid derivatives, 91. 

Acids, 82. 

Acids, aromatic, 261. 

Acrolein, 143. 

Acyl radicles, 93. 

Adjective dyes, 255. 

Alanine, 196. 

Albuminous substances, 199. 

Alcohol, ethyl, 60. 

Alcohol, preparation from grain, 175. 

Alcohol ates, 57. 

Alcohols, 56. 

Alcohols, aromatic, 260. 

Alcohols, behavior of different classes 
on oxidation, 65 to 69. 

Aldehyde ammonia, 109. 

Aldehyde resin, 109. 

Aldehydes, 103. 

Aldehydes, aromatic, 264. 

Aldohexoses, 163. 

Aldoses, 162. 

Aliphatic compounds, 34. 

Aliphatic character in aromatic com- 
pounds, 237. 



Alizarin, 284. 

Alkaloids, 293. 

Alkyl halides, 72. 

Alkyl radicles, 53. 

Allocyclic compounds, 294. 

AUyl alcohol, 131. 

Aluminium chloride synthesis, 232, 

266. 
Amides, 101, 120. 
Amines, 114. 
Amines, aromatic, 241. 
Aminoacetic acid, 193. 
Amino-acids, 193. 
Amino-acids in proteins, 201. 
Amino-group, 102. 
Ammonium cyanate, 185. 
Ammonium salts, substituted, 116. 
Ammonium sulphocyanate, 192. 
Amygdalin, 265. 
Amyl, 52. 
Amyl alcohols, 70. 
Amylene, 129. 
Amyl nitrite, 78. 
Amyloid, 176. 
Amylodextrin, 175. 
Aniline, 244. 
Aniline blue, 274. 
Aniline yellow, 253. 
Anthracene, 283. 
Anthranilic acid, 278. 
Anthraquinone, 284. 
Argol, 160. 

Aromatic compounds, 218. 
Aromatic compounds denned, 34. 
Artificial silk, 181. 
Asymmetric aromatic compounds, 

224. 
Asymmetric carbon atom, 148. 
Atomicity, 134. 
Atomic theory, 27, 303. 
Aurins, 275. 



309 



310 



INDEX 



Auxochromes, 253. 
Azo-dyes, 252, 258, 288. 
Azotometer, 16. 

Baeyer's benzene formula, 221. 

Baeyer's theory of plant assimila- 
tion, 108, 208. 

Baking powders, 160. 

Bases, 59. 

Beer, alcohol in, 63. 

Benzal chloride, 237. 

Benzaldehyde, 241, 265. 

Benzene, 219. 

Benzhydrol, 266. 

Benzine, 53. 

Benzoic acid, 261. 

Benzophenone, 266. 

Benzoquinone, 267. 

Benzotrichloride, 237. 

Benzyl, 237. 

Benzyl alcohol, 260. 

Benzylamine, 246. 

Benzyl chloride, 237. 

Bioses, 161, 170. 

Bitter almonds, oil of, 241, 265. 

Blasting gelatine, 179. 

Blood, 216. 

Boiling point, determination of, 4. 

Boiling point method of determining 
molecular weights, 27. 

Bonds, 29. 

Brombenzene, 234. 

Butanes, 48. 

Butter, 146. 

Butyl, 52. 

Butyl alcohols, 68. 

Butylene, 129. 

Butyric acids, 89. 

Butyryl, 93. 

Cadaverine, 292. 
Caffein, 191. 
Calcium acetate, 111. 
Calcium carbide, 130. 
Calcium formate, 103. 
Calcium oxalate, 139. 
Camphene, 297. 
Camphor, 179, 298. 
Candles, 143. 
Cane sugar, 171. 
Caoutchouc, 299. 



Caramel, 171. 
Carbamic acid, 187. 
Carbamide, 187. 
Carbide, calcium, 130. 
Carbinol, 69. 
Carbohydrates, 161. 
Carbolic acid, 258. 
Carbon bisulphide, 37, 191. 
Carbon, detection, 10. 
Carbon, determination, 13. 
Carbonic acid derivatives, 186. 
Carbon monoxide, 37, 86, 138. 
Carbon suboxide, 140. 
Carbon tetrachloride, 42. 
Carbonyl group, 103. 
Carboxyl group, 82. 
Casein, 203. 
Catalysis, 169. 
Celluloid, 179. 
Cellose, 176. 
Cellulose, 176. 
Cellulose acetates, 179. 
Cellulose nitrates, 178. 
Cheese, 203. 
Chloracetic acid, 139. 
Chloral, 113. 
Chloral hydrate, 113. 
Chlormethane, 39. 
Chloroform, 41, 113. 
Chlorpropionic acid, 147, 193. 
Chromophores, 252. 
Cinnamic aldehyde, 265. 
Coal-gas, 36. 
Coal-tar industry, 287. 
Collodion, 178. 
Combustions, 13. 
Condensation, 106. 
Configuration, 151. 
Continuous processes, 80. 
Cracking of oils, 54. 
Cream of tartar, 160. 
Cresols, 259. 
Crystallization, 6. 
Crystal violet, 274. 
Cyanogen, 184. 
Cyanogen derivatives, 182. 
Cymene, 231, 296. 

Dead oil, 289. 
Desiccator, vacuum, 7. 
Developers, 260. 



INDEX 



311 



Dextrin, 175. 

Dextrose, 164. 

Diastase, 173. 

Diazonium salts, 248. 

Diazoninm salts, constitution, 251. 

Diazo-reaction, 247. 

Dibasic acids, 136. 

Dichlormethane, 41. 

Dichlornaphthalenes, 282. 

Diethyl ether, 80. 

Dihydroxybenzenes, 259. 

Dimethvlamine, 116, 120. 

Dimethylaniline, 246. 

Dimethyl ether, 79. 

Diphenylamine, 247. 

Diphenylamine, basicity, 242. 

Diphenylmethane, 237. 

Distillation, 5. 

Distribution coefficient, 9. 

Double bond, 128. 

Driers, 146. 

Drying, method of, 7. 

Drying oils, 144. 

Dyeing, theories of, 254. 

Dyes, 252, 270, 284. 

Dynamite, 142. 

Electric conductivity, 100. 

Elementary analysis, 10. 

Elements in organic compounds, 10. 

Empirical formula, derivation of, 19. 

Emulsin, 265. 

Eosin, 277. 

Enantiomorphism, 150. 

Enzymes, 168. 

Equilibrium, chemical, 96. 

Esterification, 76, 96. 

Esters, 59, 76, 94. 

Esters of inorganic acids, 76. 

Ethane, 43. 

Ethers, 79. 

Ethyl, 44. 

Ethyl acetate, 99. 

Ethyl alcohol, 60. 

Ethyl amine, 120. 

Ethyl bromide, 73. 

Ethyl chloride, 44. 

Ethylene, 125. 

Ethylene bromide, 126. 

Ethylene chloride, 126. 

Ethyl iodide, 73. 



Ethyl methyl ketone, 112. 

Ethyl nitrite, 78. 

Ethyl sulphuric acid, 78, 126. 

Fats, 90, 133. 
Fatty acids, 89. 

Fehling's solution, 104, 164, 171. 
Fermentation, 167. 
Ferments, 168. 
Fibroin, 199. 
Fire-damp, 36. 
Flash-point, 54. 
Fluorescein, 277. 
Formaldehyde, 60, 107. 
Formaldehyde in plant life, 208. 
Formalin, 107. 
Formic acid, 86, 138. 
Formic acid, constitution, 82. 
Fractional distillation, 7. 
Freezing-point method of determin- 
ing molecular weights, 24. 
Fructose, 165, 172. 
Fruit sugar, 165. 
Fuchsine, 270. 
Furan, 290. 
Fusel oil, 63. 

Galactose, 165. 

Gallic acid, 260. 

Gas, coal, 36. 

Gelatin, 199. 

Glucosazone, 166. 

d-Glucose, 164, 172, 265. 

Glucose, commercial, 165, 175. 

Glucosides, 173. 

Glycerin, 141. 

Glycine, 194. 

Glycocoll, 194. 

Glycogen, 211. 

Glycol, 135. 

Grape sugar, 164. 

Graphic formulae, 27. 

Gums, 175. 

Gun-cotton, 178. 

Gutta percha, 302. 

Haemoglobin, 200, 216. 
Halogen compounds, aliphatic, 72. 
Halogen compounds, aromatic, 234. 
Halogens, detection, 11. 
Halogens, determination, 18. 



312 



INDEX 



Helianthin, 254. 

Heterocyclic compounds, 290. 

Hexacontane, 51. 

Hexanes, 50. 

Hexyl, 52. 

Hexyl iodide, 163. 

Hippuric acid, 210. 

Homologous series, 44, 50. 

Honey, 172. 

Honey stone, 263. 

Hydrazine, 249. 

Hydrazobenzene, 252. 

Hydrazones, 249. 

Hydroaromatic compounds, 294. 

Hj'drocarbons, aliphatic saturated, 
34. 

Hydrocarbons, aliphatic unsatu- 
rated, 124. 

Hydrocarbons, allocyclic, 279. 

Hydrocarbons, aromatic, 230. 

Hydrocyanic acid, 183. 

Hydrogen, detection, 11. 

Hydrogen, determination, 12. 

Hydrolysis, 77, 100. 

Hydroquinone, 259, 267. 

Hydroxy-acids, 105, 147. 

Hydroxylamine, 106. 

India-rubber, 299. 
Indigo, 277. 
Indigo-white, 277. 
Indoxyl, 279. 
Inversion of sugar, 172. 
Invertase, 172. 
Invert-sugar, 172. 
Iodoform, 114. 
Isobutyl alcohol, 68. 
Isobutyl carbinol, 70. 
Isobutyric acid, 90. 
Isomaltose, 173. 
Isomerism, 27. 
Isonitriles, 75. 
Isopropyl alcohols, 64. 
Isopropyl iodide, 46. 

Kekule's benzene formula, 221, 228. 

Keratin, 199. 

Kerosene, 54. 

Ketohexoses, 163. 

Ketones, 111. 

Ketones, aromatic, 265, 



Ketones, behavior on oxidation, 67. 
Ketoses, 162. 

Lactic acid, 147. 
Lactonitrile, 147. 
Lactose, 172. 
Lakes, 285. 
Lard, 142. 
Lead formate, 86. 
Leucine, 197. 
Leuko-compounds, 268. 
Levulinic acid, 301. 
Levulose, 165. 
Ligroin, 53. 
Limonene, 296. 
Linoleic acid, 145. 
Linolinic acid, 145. 
Linseed oil, 145. 

Madder, 284. 

Magenta, 270. 

Malachite green, 274. 

Malonic acid, 139. 

Malt, 175. 

Maltose, 172. 

Marsh gas, 36. 

Mass action law, 96. 

Mauve, 287. 

Melinite, 259. 

Millitic acid, 263. 

Melting point, determination of, 6. 

Menthol, 297. 

Mercerization, 177. 

Mercuric cyanide, 184. 

Mercury sulphocyanate, 185. 

Mesotartaric acid, 156. 

Mesitylene, 231. 

Metabolism, 208, 210. 

Meta position, 223. 

Metaldehyde, 109. 

Methane, 36. 

Methane series, 36, 44. 

Methyl, 40. 

Methyl alcohol, 56. 

Methylamine, 116, 120. 

Methyl aniline, 246. 

Methyl chloride, 40, 57. 

Methylene, 41. 

Methyl ethyl ether, 81. 

Methyl iodide, 40, 73. 

Methyl orange, 254. 



INDEX 



313 



Methyl sulphate, 78. 
Milk sugar, 165, 172. 
Molecular weight, methods of deter- 
mining, 20. 
Monoses, 161. 
Mordants, 285. 
Mother of vinegar, 89. 

Naphtha, 53. 

Naphthalene, 280. 

Naphthols, 282. 

Naphthylamines, 282. 

Nitration, 220. 

Nitriles, 75, 101, 119. 

Nitriles, aromatic, 249. 

Nitro-cellulose, 177. 

Nitro-compounds, 240. 

Nitrobenzene, 240. 

Nitrogen cycle, 207. 

Nitrogen, detection, 11. 

Nitrogen, determination, 15. 

Nitroglycerin, 141. 

Nitro-group, 220. 

Nitrosamines, 119. 

Nomenclature, general principles, 42. 

Normal compounds, 47. 

Olefiant gas, 126. 

defines, 126. 

Oleic acid, 133, 142. 

Olein, 142. 

Oleomargarine, 146. 

Opium bases, 286. 

Optical isomerism, 70, 147. 

Optical superposition, principle of, 

154. 
Orientation, 228. 
Ortho position, 223. 
Oxalic acid, 136. 
Oximes, 106. 
Oxyhemoglobin, 216. 
Oxytrimethylenes, 108. 
Ozonides, 300. 

Palmitic acid, 90, 142. 
Palmitin, 142. 
Para position, 223. 
Paraffin, 54. 
Paraffin series, 36. 
Paraformaldehyde, 107. 
Parafuchsine, 272, 



Paraldehyde, 109. 

Paraleukaniline, 271. 

Pararosaniline, 270. 

Pentanes, 49. 

Pentoses, 162, 175. 

Peppermint, oil of, 297. 

Pepsin, 168. 

Petroleum, 53. 

Petroleum ether, 53. 

Pharaoh's serpents, 185. 

Phenanthrene, 286. 

Phenol, 258. 

Phenols, 239, 249, 257. 

Phenolphthalein, 276. 

Phenyl, 235. 

Phenyl hydrazine, 166, 249. 

Phosgen/l86. 

Photography, 260. 

Phthaleins, 275. 

Phthalic acids, 263, 281. 

Phthalimid, 278. 

Picric acid, 258. 

Pinene, 146, 297. 

Piperazines, 190. 

Piperidine, 292. 

Polyatomic alcohols, 134. 

Polymerization, 105. 

Polyoses, 173. 

Polypeptides, 199. 

Positive and negative radicles, 242. 

Potassium cyanide, 183. 

Potassium ferricyanide, 182. 

Potassium ferrocyanide, 182. 

Powder, smokeless, 179. 

Primary alcohols, 64. 

Primary amines, 115, 118. 

Primary carbon atom, 46. 

Propane, 45. 

Propionic acid, 89. 

Propionyl, 93. 

Propyl alcohol, 64. 

Propylene, 129. 

Propyl iodides, 46, 68, 73. 

Proteins, 199. 

Prussian blue, 183. 

Prussic acid, 183. 

Ptyalin, 210. 

Purification of organic compounds, 4. 

Purin, 190. 

Purity, criteria of, 4. 

Pyridine, 290. 



314 



INDEX 



Pyrocateehoi, 259. 
Pyrogallol, 260. 
Pyroligneous acid, 112. 
Pyroxylene, 178. 
Pyrrole, 290. 

Qualitative analysis of organic com- 
pounds, 9. 
Quantitative analysis, 12. 
Quaternary carbon atom, 46. 
Quinoid structure, 268. 
Quinoline, 293. 
Quinones, 267. 

Racemic acid, 156. 
Racemic compounds, 153. 
Radicles, 40. 
Resorcinol, 259. 
Reversible reactions, 97, 99. 
Rochelle salt, 160. 
Rosaniline, 270. 
Rosolic acid, 275. 

Saccharin, 262. 

Salicylic acid, 262. 

Saponification, 77, 96, 143. *" 

Saturated hydrocarbons, 34. 

Secondary alcohols, 66. 

Secondary amides, 120. 

Secondary amines, 115. 

Secondary butyl alcohol, 70. 

Secondary carbon atom, 46. 

Secondary propyl alcohol, 66. 

Separatory funnel, 9. 

Side-chain, 233. 

Silk, artificial, 181. 

Smokeless powder, 179. 

Soaps, 90, 143. 

Sodium acetate, 37. 

Sodium ethylate, 61. 

Sodium formate, 86. 

Sodium methylate, 57. 

Sodium nitro-prusside, reagent for 

sulphur, 12. 
Sodium phenolate, 262. 
Sodium propionate, 43. 
Solubilities of organic compounds, 2 
Soluble starch, 175. 
Solvents, organic, 2. 
Spermaceti, 100. 
Starch, 63, 165, 174. 



Starch iodide, 174. 
Steam, distillation with, 8. 
Stearic acid, 90, 142. 
Stearin, 142. 
Stearin candles, 143. 
Stereo-isomerism, 151. 
Structure theory, 303. 
Substantive dyes, 255. 
Substitution, 31, 39. 
Succinic acid, 140. 
Sucrose, 171. 
Sugar, cane, 171. 
Sugars, 161. 
Sulphanilic acid, 254. 
Sulphobentfoic acid, 262. 
Sulphocyanates, 185. 
Sulpho-group, 220. 
Sulphonation, 220. 
Sulphonic acids, 238, 257. 
Sulphur, detection, 12. 
Sulphur, determination, 18. 
Sulphuric ether, 80. 
Sweet spirits of niter, 78. 
Symmetrical compounds, aromatic, 

Tallow, 143. 

Tartar emetic, 160. 

Tartaric acids, 156. 

Terephthalic acid, 295. 

Terpenes, 296. 

Tertiary alcohols, 68. 

Tertiary amides, 120. 

Tertiary amines, 115. 

Tertiary butyl alcohol, 68. 

Tertiary carbon atom, 46. 

Tetrahedral models, 149. 

Tetramethyl ammonium salts, 117 

Tetroses, 162. 
Theobromin, 191. 
Thiophene, 290. 
Toluene, 230, 237. 
Toluidines, 245. 
Triatomic alcohols, 141. 
Trichloracetaldehyde, 113. 
Trichloracetone, 113. 
Trimethylamine, 120. 
Trimethylene, 294. 
Trimethylmethane, 48. 
Trioses, 161. 
Triphenylamine, 243. 



INDEX 



315 



Triphenyl carbinol, 274. 
Triphenylmethane, 271. 
Triphenylmethane dyes, 270. 
Triple bonds, 129. 
Trisubstitution products of benzene, 

226. 
Trivial names, 43. 
Turnbull's blue, 183. 
Turpentine, 146, 297. 



Vapor density, method of deter- 
mining, 21. 

Velocity of reaction in organic com- 
pounds, 3. 

Vicinal position, 224. 

Vinegar, 89. 

Vital force, 3, 188. 

Vital processes, chemistry of, 204. 

Vulcanization of rubber, 191, 300. 



Ultimate analysis, 10. 
Unsaturated compounds, 131. 
Uranin, 277. 
Urea, 187. 
Uric acid, 189. 

Vacuum desiccator, 7. 
Valence theory, 28, 303. 
Valence, variable, 37. 
Valine, 197. 
Vanillin, 265. 



Waxes, 71, 100. 

Wine, determination of alcohol in, 

63. 
Wintergreen, oil of, 263. 
Wood distillate, 88. 
Wood spirit, 56. 

Xylenes, 230. 

Yeast, 63, 167. 

Zymase, 63, 169. 



Short-title Catalogue 

OF THE 

PUBLICATIONS 

OF 

JOHN WILEY & SONS 

New York 
London: CHAPMAN & HALL, Limited 



ARRANGED UNDER SUBJECTS 



Descriptive circulars sent on application. Books marked with an asterisk (*) are 
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* Ludlow's Logarithmic and Trigonometric Tables 8vo, 

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Washington's Manual of the Chemical Analysis of Rocks 8vo, 

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Wait's Engineering and Architectural Jurisprudence 8vo, $6 00 

Sheep, 6 50 

Law of Contracts 8vo, 3 00 

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Architecture 8vo, 5 00 

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* Waterbury's Vest-Pocket Hand-book of Mathematics for Engineers. 

2|X5f inches, mor. 1 00 
Webb's Problem's in the Use and Adjustment of Engineering Instruments. 

16mo, mor. 1 25 

Wilson's Topographic Surveying 8vo, 3 50 



BRIDGES AND ROOFS. 

Boiler's Practical Treatise on the Construction of Iron Highway Bridges.. 8vo, 

* Thames River Bridge Oblong paper, 

Burr and Falk's Design and Construction of Metallic Bridges 8vo, 

Influence Lines for Bridge and Roof Computations 8vo, 

Du Bois's Mechanics of Engineering. Vol. II Small 4to, 

Foster's Treatise on Wooden Trestle Bridges 4to, 

Fowler's Ordinary Foundations 8vo, 

Greene's Arches in Wood, Iron, and Stone 8vo, 

Bridge Trusses 8vo, 

Roof Trusses 8vo, 

Grimm's Secondary Stresses in Bridge Trusses 8vo, 

Heller's Stresses in Structures and the Accompanying Deformations.. . ,8vo, 

Howe's Design of Simple Roof-trusses in Wood and Steel 8vo. 

Symmetrical Masonry Arches 8vo, 

Treatise on Arches 8vo, 

Johnson, Bryan and Turneaure's Theory and Practice in the Designing of 

Modern Framed Structures Small 4to, 

Merriman and Jacoby's Text-book on Roofs and Bridges: 

Part I. Stresses in Simple Trusses 8vo, 

Part II. Graphic Statics 8vo, 

Part III. Bridge Design 8vo, 

Part IV. Higher Structures 8vo, 

Morison's Memphis Bridge Oblong 4to, 

Sondericker's Graphic Statics, with Applications to Trusses, Beams, and 

Arches 8vo, 

Waddell's De Pontibus, Pocket-book for Bridge Engineers 16mo, mor. 

* Specifications for Steel Bridges 12mo, 

Waddell and Harringtoon's Bridge Engineering. (In Preparation.) 

Wright's Designing of Draw-spans. Two parts in one volume 8vo, 3 50 



HYDRAULICS. 

Barnes's Ice Formation 8vo, 3 00 

Bazin's Experiments upon the Contraction of the Liquid Vein Issuing from 

an Orifice. (Trautwine.) 8vo, 2 00 

Bovey 's Treatise on Hydraulics 8vo, 5 00 

Church's Diagrams of Mean Velocity of Water in Open Channels. 

Oblong 4to, paper, 1 50 

Hydraulic Motors 8vo, 2 00 

Coffin's Graphical Solution of Hydraulic Problems ' 16mo, mor. 2 50 ■ 

Flather's Dynamometers, and the Measurement of Power 12mo, 3 00 

Folwell's Water-supply Engineering 8vo, 4 00 

Frizell's Water-power 8vo, 5 00 

Fuertes's Water and Public Health 12mo, 1 50 

Water-filtration Works 12mo, 2 50 

Ganguillet and Kutter's General Formula for the Uniform Flow of Water in 

Rivers and Other Channels. (Hering and Trautwine.) 8vo, 4 00 

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Hazen's Clean Water and How to Get It Large 12mo, $1 50 

Filtration of Public Water-supplies 8vo, 3 00 

Hazelhurst's Towers and Tanks for Water-works 8vo, 2 50 

Herschel's 115 Experiments on the Carrying Capacity of Large, Riveted, Metal 

Conduits 8vo, 2 00 

Hoyt and Grover's River Discharge 8vo, 2 00 

Hubbard and Kiersted's Water-works Management and Maintenance. 

8vo, 4 00 

* Lyndon's Development and Electrical Distribution of Water Power. 

8vo, 3 00 
Mason's Water-supply. (Considered Principally from a Sanitary Stand- 
point.) 8vo, 

Merriman's Treatise on Hydraulics 8vo, 

* Molitor's Hydraulics of Rivers, Weirs and Sluice:; 8vo, 

* Richards's Laboratory Notes on Industrial Water Analysis 8vo, 

Schuyler's Reservoirs for Irrigation, Water-power, and Domestic Water- 
supply. Second Edition, Revised and Enlarged Large 8vo, 

* Thomas and Watt's Improvement of Rivers 4to, 

Turneaure and Russell's Public Water-supplies 8vo, 

Wegmann's Design and Construction of Dams. 5th Ed., enlarged 4to, 

Water-Supply of the City of New York from 1658 to 1895 4to, 

Whipple's Value of Pure Water Large 12mo, 

Williams and Hazen's Hydraulic Tables 8vo, 

Wilson's Irrigation Engineering 8vo, 

Wood's Turbines 8vo, 



MATERIALS OF ENGINEERING. 

Baker's Roads and Pavements 8vo, 5 00 

Treatise on Masonry Construction 8vo, 5 00 

Black's United States Public Works Oblong 4to, 5 00 

Blanchard's Bituminous Roads. (In Press.) 

Bleininger's Manufacture of Hydraulic Cement. (In Preparation.) 

* Bovey's Strength of Materials and Theory of Structures 8vo, 7 50 

Burr's Elasticity and Resistance of the Materials of Engineering 8vo, 7 50 

Byrne's Highway Construction 8vo, 5 00 

Inspection of the Materials and Workmanship Employed in Construction. 

16mo, 3 00 

Church's Mechanics of Engineering 8vo, 6 00 

Du Bois's Mechanics of Engineering. 

Vol. I. Kinematics, Statics, Kinetics Small 4to, 7 50 

Vol. II. The Stresses in Framed Structures, Strength of Materials and 
Theory of Flexures Small 4to, 

* Eckel's Cements, Limes, and Plasters 8vo, 

Stone and Clay Products used in Engineering. (In Preparation.) 
Fowler's Ordinary Foundations 8vo, 

* Greene's Structural Mechanics 8vo, 

* Holley's Lead and Zinc Pigments Large 12mo, 

Holley and Ladd's Analysis of Mixed Paints, Color Pigments and Varnishes. 

Large 12mo, 
Johnson's (C. M.) Rapid Methods for the Chemical Analysis of Special Steels, 

Steel-making Alloys and Graphite Large 12mo, 

Johnson's (J. B.) Materials of Construction Large 8vo, 

Keep's Cast Iron 8vo, 

Lanza's Applied Mechanics r - 8vo, 

Maire's Modern Pigments and their Vehicles 12mo, 

Martens's Handbook on Testing Materials. (Henning.) 2 vols .8vo, 

Maurer's Technical Mechanics 8vo, 

Merrill's Stones for Building and Decoration. 8vo, 

Merriman's Mechanics of Materials 8vo, 

* Strength of Materials 12mo, 

Metcalf 's Steel. A Manual for Steel-users 12mo, 

Morrison's Highway Engineering 8vo, 

Patton's Practical Treatise on Foundations 8vo, 

Rice's Concrete Block Manufacture 8vo, 



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Richardson's Modern Asphalt Pavements 8vo, $3 00 

Richey's Building Foreman's Pocket Book and Ready Reference. 16mo,mor. 5 00 

* Cement Workers' and Plasterers' Edition (Building Mechanics' Ready 

Reference Series) 16mo, mor. 1 50 

Handbook for Superintendents of Construction 16mo, mor. 4 00 

* Stone and Brick Masons' Edition (Building Mechanics' Ready 

Reference Series) 16mo, mor. 1 50 

* Ries's Clays: Their Occurrence, Properties, and Uses 8vo, 5 00 

* Ries and Leighton's History of the Clay-working Industry of the United 

States 8vo. 2 50 

Sabin's Industrial and Artistic Technology of Paint and Varnish 8vo, 3 00 

Smith's Strength of Material 12mo, 

Snow's Principal Species of Wood 8vo, 3 50 

Spalding's Hydraulic Cement 12mo, 2 00 

Text-book on Roads and Pavements 12mo, 2 00 

Taylor and Thompson's Treatise on Concrete, Plain and Reinforced 8vo, 5 00 

Thurston's Materials of Engineering. In Three Parts 8vo, 8 00 

Part I. Non-metallic Materials of Engineering and Metallurgy.. . .8vo, 2 00 

Part II. Iron and Steel 8vo, 3 50 

Part III. A Treatise on Brasses, Bronzes, and Other Alloys and their 

Constituents 8vo, 2 50 

Tillson's Street Pavements and Paving Materials 8vo, 4 00 

Turneaure and Maurer's Principles of Reinforced Concrete Construction. 

Second Edition, Revised and Enlarged 8vo, 3 50 

Waterbury's Cement Laboratory Manual. . 12mo, 1 00 

Wood's (De V.) Treatise on the Resistance of Materials, and an Appendix on 

the Preservation of Timber 8vo, 2 00 

Wood's (M. P.) Rustless Coatings: Corrosion and Electrolysis of Iron and 

Steel 8vo, 4 00 



RAILWAY ENGINEERING. 

Andrews's Handbook for Street Railway Engineers 3X5 inches, mor. 

Berg's Buildings and Structures of American Railroads .4to, 

Brooks's Handbook of Street Railroad Location 16mo, mor. 

Butts's Civil Engineer's Field-book 16mo, mor. 

Crandall's Railway and Other Earthwork Tables 8vo, 

Transition Curve 16mo, mor. 

* Crockett's Methods for Earthwork Computations 8vo, 

Dredge's History of the Pennsylvania Railroad. (1879) Paper 

Fisher's Table of Cubic Yards Cardboard, 

Godwin's Railroad Engineers' Field-book and Explorers' Guide. . 16mo, mor. 
Hudson's Tables for Calculating the Cubic Contents of Excavations and Era- 

bankmen ts 8vo, 

Ives and Hilts's Problems in Surveying, Railroad Surveying and Geodesy 

16mo, mor. 

Molitor and Beard's Manual for Resident Engineers 16mo, 

Nagle's Field Manual for Railroad Engineers 16mo, mor. 

* Orrock's Railroad Structures and Estimates 8vo, 

Philbrick's Field Manual for Engineers 16mo, mor. 

Raymond's Railroad Engineering. 3 volumes. 

Vol. I. Railroad Field Geometry. (In Preparation.) 

Vol. II. Elements of Railroad Engineering 8vo, 3 50 

Vol. III. Railroad Engineer's Field Book. (In Preparation.) 
Searles's Field Engineering 16mo, mor. 3 00 

Railroad Spiral 16mo, mor. 1 50 

Taylor's Prismoidal Formula? and Earthwork 8vo, i 50 

* Trautwine's Field Practice of Laying Out Circular Curves for Railroads. 

12mo, mor. 2 50 
* Method of Calculating the Cubic Contents of Excavations and Em- 
bankments by the Aid of Diagrams 8vo, 2 00 

Webb's Economics of Railroad Construction Large 12mo, 2 50 

Railroad Construction 16mo, mor. 5 00 

Wellington's Economic Theory of the Location of Railways Large 12mo, 5 00 

Wilson's Elements of Railroad-Track and Construction 12mo, 2 00 

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DRAWING. 

Barr's Kinematics of Machinery 8vo, $2 50 

* Bartlett's Mechanical Drawing 8vo, 3 00 

* " " " Abridged Ed 8vo, 150 

Coolidge's Manual of Drawing 8vo, paper, 1 00 

Coolidge and Freeman's Elements of General Drafting for Mechanical Engi- 
neers Oblong 4to, 2 50 

Durley's Kinematics of Machines 8vo, 4 00 

Emch's Introduction to Projective Geometry and its Application 8vo, 2 50 

French and Ives' Stereotomy 8vo, 2 50 

Hill's Text-book on Shades and Shadows, and Perspective 8vo, 2 00 

Jamison's Advanced Mechanical Drawing Svo, 2 00 

Elements of Mechanical Drawing 8vo, 2 50 

Jones's Machine Design: 

Part I. Kinematics of Machinery 8vo, 1 50 

Part II. Form, Strength, and Proportions of Parts . 8vo, 3 00 

Kimball and Barr's Machine Design. (In Press.) 

MacCord's Elements of Descritpive Geometry 8vo, 3 00 

Kinematics; or, Practical Mechanism 8vo, 5 00 

Mechanical Drawing 4to, 4 00 

Velocity Diagrams. : 8vo, 1 50 

McLeod's Descriptive Geometry Large 12mo, 1 50 

* Mahan's Descriptive Geometry and Stone-cutting 8vo, 1 50 

Industrial Drawing. (Thompson.) 8vo, 3 50 

Moyer's Descriptive Geometry 8vo, 2 00 

Reed's Topographical Drawing and Sketching 4to, 5 00 

Reid's Course in Mechanical Drawing 8vo, 2 00 

Text-book of Mechanical Drawing and Elementary Machine Design.. 8vo, 3 00 

Robinson's Principles of Mechanism 8vo, 3 00 

Schwamb and Merrill's Elements of Mechanism 8vo, 3 00 

Smith (A. W.) and Marx's Machine Design 8vo, 3 00 

Smith's (R. S.) Manual of Topographical Drawing. (McMillan) 8vo, 2 50 

* Titsworth's Elements of Mechanical Drawing. Oblong 8vo, 1 25 

Warren's Drafting Instruments and Operations 12mo, 1 25 

Elements of Descriptive Geometry, Shadows, and Perspective 8vo, 3 50 

Elements of Machine Construction and Drawing 8vo, 7 50 

Elements of Plane and Solid Free-hand Geometrical Drawing. . . . 12mo, 1 00 

General Problems of Shades and Shadows 8vo, 3 00 

Manual of Elementary Problems in the Linear Perspective of Forms and 

Shadow, 12mo, 1 00 

Manual of Elementary Projection Drawing 12mo, 1 50 

Plane Problems in Elementary Geometry 12mo, 1 25 

Problems, Theorems, and Examples in Descriptive Geometry 8vo, 2 50 

Weisbach's Kinematics and Power of Transmission. (Hermann and 

Klein . ) 8vo, 5 00 

Wilson's (H. M.) Topographic Surveying 8vo, 3 50 

* Wilson's (V. T.) Descriptive Geometry 8vo, 1 50 

Free-hand Lettering 8vo, 1 00 

Free-hand Perspective 8vo, 2 50 

Woolf's Elementary Course in Descriptive Geometry Large 8vo, 3 00 



ELECTRICITY AND PHYSICS. 

* Abegg's Theory of Electrolytic Dissociation, (von Ende.) 12mo, 1 25 

Andrews's Hand-book for Street Railway Engineering 3X5 inches, mor. 1 25 

Anthony and Brackett's Text-book of Physics. (Magie.) ... .Large 12mo, 3 00 
Anthony and Ball's Lecture-notes on the Theory of Electrical Measure- 
ments 12mo, 1 00 

Benjamin's History of Electricity 8vo, 3 00 

Voltaic Cell 8vo, 3 00 

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Betts's Lead Refining and Electrolysis 8vo, $4 00 

Classen's Quantitative Chemical Analysis by Electrolysis. (Boltwood.).8vo, 3 00 

* Collins's Manual of Wireless Telegraphy and Telephony 12mo, 1 50 

Mor. 2 00 

Crehore and Squier's Polarizing Photo-chronograph 8vo, 3 00 

* Danneel's Electrochemistry. (Merriam.) 12mo, 1 25 

Dawson's "Engineering" and Electric Traction Pocket-book. . . . 16mo, mor. 5 00 
Dolezalek's Theory of the Lead Accumulator (Storage Battery), (von Ende.) 

12mo, 2 50 

Duhem's Thermodynamics and Chemistry. (Burgess.) 8vo, 4 00 

Flather's Dynamometers, and the Measurement of Power 12mo, 3 00 

Getman's Introduction to Physical Science 12mo, 

Gilbert's De Magnete. (Mottelay) 8vo, 2 50 

* Hanchett's Alternating Currents 12mo, 1 00 

Hering's Ready Reference Tables (Conversion Factors) 16mo, mor. 2 50 

* Hobart and Ellis's High-speed Dynamo Electric Machinery 8vo, 6 00 

Holman's Precision of Measurements 8vo, 2 00 

Telescopic Mirror-scale Method, Adjustments, and Tests.. . .Large 8vo, 75 

* Karapetoff 's Experimental Electrical Engineering 8vo, 6 00 

Kinzbrunner's Testing of Continuous-current Machines 8vo, 2 00 

Landauer's Spectrum Analysis. (Tingle.) 8vo, 3 00 

Le Chatelier's High-temperature Measurements. (Boudouard — Burgess. )12mo, 3 00 

Lob's Electrochemistry of Organic Compounds. (Lore.nz) 8vo, 3 00 

* Lyndon's Development and Electrical Distribution of Water Power. .8vo, 3 00 

* Lyons's Treatise on Electromagnetic Phenomena. Vols, I .and II. 8vo, each, 6 00 

* Michie's Elements of Wave Motion Relating to Sound and Light 8vo, 4 00 

Morgan's Outline of the Theory of Solution and its Results 12mo, 1 00 

* Physical Chemistry for Electrical Engineers 12mo, 1 50 

* Norris's Introduction to the Study of Electrical Engineering 8vo, 2 50 

Norris and Denmson's Course of Problems on the Electrical Characteristics of 

Circuits and Machines. (In Press.) 

* Parshall and Hobart's Electric Machine Design 4to, half mor, 12 50 

Reagan's Locomotives: Simple, Compound, and Electric. New Edition. 

Large 12mo, 3 50 

* Rosenberg's Electrical Engineering. (Haldane Gee — Kinzbrunner.) . .8vo, 2 00 

Ryan, Norris, and Hoxie's Electrical Machinery. Vol. 1 8vo, 2 50 

Schapper's Laboratory Guide for Students in Physical Chemistry 12mo, 1 00 

* Tillman's Elementary Lessons in Heat 8vo, 1 50 

Tory and Pitcher's Manual of Laboratory Physics Large 12mo, 2 00 

Ulke's Modern Electrolytic Copper Refining 8vo, 3 00 



LAW. 

* Brennan's Hand-book of Useful Legal Information for Business Men. 

16mo, mor. 

* Davis's Elements of Law 8vo, 

* Treatise on the Military Law of United States 8vo, 

* Dudley's Military Law and the Procedure of Courts-martial. . Large 12mo, 

Manual for Courts-martial 16mo, mor. 

Wait's Engineering and Architectural Jurisprudence 8vo, 

Sheep, 

Law of Contracts 8vo , 

Law of Operations Preliminary to Construction in Engineering and 

Architecture 8vo, 

Sheep, 



MATHEMATICS. 

Baker's Elliptic Functions 8vo, 1 50 

Briggs's Elements of Plane Analytic Geometry. (Bocher) 12mo, 1 00 

* Buchanan's Plane and Spherical Trigonometry 8vo, 1 00 

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Byerley's Harmonic Functions '. 8vo, $1 00 

Chandler's Elements of the Infinitesimal Calculus 12mo, 

* Coffin's Vector Analysis 12mo, 

Compton's Manual of Logarithmic Computations 12mo, 

* Dickson's College Algebra Large 12mo, 

* Introduction to the Theory of Algebraic Equations Large 12mo, 

Emch's Introduction to Projective Geometry and its Application 8vo, 

Fiske's Functions of a Complex Variable 8vo, 

Halsted's Elementary Synthetic Geometry 8vo, 

Elements of Geometry 8vo, 

* Rational Geometry 12mo, 

Synthetic Projective Geometry 8vo, 

Hyde's Grassmann's Space Analysis 8vo, 

* Johnson's (J. B.) Three-place Logarithmic Tables: Vest-pocket size, paper, 

* 100 copies, 
* Mounted on heavy cardboard, 8 X 10 inches, 

* 10 copies, 
Johnson's (W. W.) Abridged Editions of Differential and Integral Calculus. 

Large 12mo, 1 vol. 

Curve Tracing in Cartesian Co-ordinates 12mo, 

Differential Equations 8vo, 

Elementary Treatise on Differential Calculus Large 12mo, 

Elementary Treatise on the Integral Calculus. Large 12mo, 

* Theoretical Mechanics 1 2mo, 

Theory of Errors and the Method of Least Squares 1 2mo, 

Treatise on Differential Calculus Large 12mo, 

Treatise on the Integral Calculus Large 12mo, 

Treatise on Ordinary and Partial Differential Equations. . .Large 12mo, 

Karapetoff's Engineering Applications of Higher Mathematics. 

(In Preparation.) 
Laplace's Philosophical Essay on Probabilities. (Truscott and Emory.) . 12mo, 2 00 

* Ludlow and Bass's Elements of Trigonometry and Logarithmic and Other 

Tables 8vo, 3 00 

* Trigonometry and Tables published separately Each, 2 00 

* Ludlow's Logarithmic and Trigonometric Tables 8vo, 1 00 

Macfarlane's Vector Analysis and Quaternions 8vo, 1 00 

McMahon's Hyperbolic Functions 8vo, 1 00 

Manning's Irrational Numbers and their Representation by Sequences and 

Series 12mo, 1 25 

Mathematical Monographs. Edited by Mansfield Merriman and Robert 

S. Woodward Octavo, each 1 00 

No. 1. History of Modern Mathematics, by David Eugene Smith. 
No. 2. Synthetic Projective Geometry, by George Bruce Halsted. 
No. 3. Determinants, by Laenas Gifford Weld. No. 4. Hyper- 
bolic Functions, by James McMahon. No. 5. Harmonic Func- 
tions, by William E. Byerly. No. 6. Grassmann's Space Analysis, 
by Edward W. Hyde. No. 7. Probability and Theory of Errors, 
by Robert S. Woodward. No. 8. Vector Analysis and Quaternions, 
by Alexander Macfarlane. No. 9. Differential Equations, by 
William Woolsey Johnson. No. 10. The Solution of Equations, 
by Mansfield Merriman. No. 11. Functions of a Complex Variable, 
by Thomas S. Fiske. 

Maurer's Technical Mechanics 8vo, 

Merriman's Method of Least Squares 8vo, 

Solution of Equations 8vo, 

Rice and Johnson's Differential and Integral Calculus. 2 vols, in one. 

Large 12mo, 

Elementary Treatise on the Differential Calculus Large 12mo, 

Smith's History of Modern Mathematics 8vo, 

* Veblen and Lennes's Introduction to the Real Infinitesimal Analysis of One 

Variable 8vo, 

* Waterbury's Vest Pocket Hand-book of Mathematics for Engineers. 

2$ X 5| inches, mor. 

Weld's Determinants 8vo, 

Wood's Elements of Co-ordinate Geometry 8vo, 

Woodward's Probability and Theory of Errors 8vo, 

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MECHANICAL ENGINEERING. 

MATERIALS OF ENGINEERING, STEAM-ENGINES AND BOILERS. 

Bacon's Forge Practice 12mo, 

Baldwin's Steam Heating for Buildings 12mo, 

Barr's Kinematics of Machinery 8vo, 

* Bartlett's Mechanical Drawing 8vo, 

* " " " Abridged Ed 8vo, 

* Burr's Ancient and Modern Engineering and the Isthmian Canal 8vo, 

Carpenter's Experimental Engineering 8vo, 

Heating and Ventilating Buildings 8vo, 

Clerk's Gas and Oil Engine. (New edition in press.) 

Compton's First Lessons in Metal Working 12mo, 

Compton and De Groodt's Speed Lathe ". 12mo, 

Coolidge's Manual of Drawing 8vo, paper, 

Coolidge and Freeman's Elements of Geenral Drafting for Mechanical En- 
gineers Oblong 4to, 

Cromwell's Treatise on Belts and Pulleys 12mo, 

Treatise on Toothed Gearing 12mo, 

Dingey's Machinery Pattern Making 12mo, 

Durley's Kinematics of Machines 8vo, 

Flanders's Gear-cutting Machinery Large 12mo, 

Flather's Dynamometers and the Measurement of Power 12mo, 

Rope Driving 12mc, 

Gill's Gas and Fuel Analysis for Engineers 12mo, 

Goss's Locomotive Sparks 8vo, 

Greene's Pumping Machinery. (In Preparation.) 

Hering's Ready Reference Tables (Conversion Factors) 16mo, mor. 

* Hobart and Ellis's High Speed Dynamo Electric Machinery 8vo, 

Hutton's Gas Engine 8vo, 

Jamison's Advanced Mechanical Drawing 8vo, 

Elements of Mechanical Drawing 8vo, 

Jones's Gas Engine 8vo, 

Machine Design: 

Part I. Kinematics of Machinery 8vo, 

Part II. Form, Strength, and Proportions of Parts 8vo, 

Kent's Mechanical Engineer's Pocket-Book 16mo, mor. 

Kerr's Power and Power Transmission 8vo, 

Kimball and Barr's Machine Design. (In Press.) 

Levin's Gas Engine. (In Press.) 8vo, 

Leonard's Machine Shop Tools and Methods 8vo, 

* Lorenz's Modern Refrigerating Machinery. (Pope, Haven, and Dean). . 8vo, 
MacCord's Kinematics; or, Practical Mechanism 8vo, 

Mechanical Drawing 4to, 

Velocity Diagrams 8vo, 

MacFarland's Standard Reduction Factors for Gases. . . 8vo, 

Mahan's Industrial Drawing. (Thompson.) 8vo, 

Mehrtens's Gas Engine Theory and Design Large 12mo, 

Oberg's Handbook of Small Tools Large 12mo, 

* Parshall and Hobart's Electric Machine Design. Small 4to, half leather, 

Peele's Compressed Air Plant for Mines 8vo, 

Poole's Calorific Power of Fuels 8vo, 

* Porter's Engineering Reminiscences, 1855 to 1882 8vo, 

Reid's Course in Mechanical Drawing 8vo, 

Text-book of Mechanical Drawing and Elementary Machine Design. 8vo, 

Richards's Compressed Air 12mo, 

Robinson's Principles of Mechanism 8vo, 

Schwamb and Merrill's Elements of Mechanism 8vo, 

Smith (A. W.) and Marx's Machine Design 8vo, 

Smith's (0.) Press-working of Metals 8vo, 

Sorel's Carbureting and Combustion in Alcohol Engines. (Woodward and 

Preston.) Large 12mo, 

Stone's Practical Testing of Gas and Gas Meters 8vo, 

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Thurston's Animal as a Machine and Prime Motor, and the Laws of Energetics. 

12mo, 
Treatise on Friction and Lost Work in Machinery and Mill Work . . . 8vo, 

* Tillson's Complete Automobile Instructor 16mo, 

* Titsworth's Elements of Mechanical Drawing Oblong 8vo, 

Warren's Elements of Machine Construction and Drawing 8vo, 

* Waterbury's Vest Pocket Hand-book of Mathematics for Engineers. 

2|X5| inches, mor. 
Weisbach's Kinematics and the Power of Transmission. (Herrmann — 

Klein.) 8vo, 

Machinery of Transmission and Governors. (Hermann — Klein.). .8vo, 
Wood's Turbines 8vo, 



MATERIALS OF ENGINEERING. 

* Bovey's Strength of Materials and Theory of Structures 8vo, 

Burr's Elasticity and Resistance of the Materials of Engineering 8vo, 

Church's Mechanics of Engineering 8vo, 

* Greene's Structural Mechanics 8vo, 

* Holley's Lead and Zinc Pigments Large 12mo 

Holley and Ladd's Analysis of Mixed Paints, Color Pigments, and Varnishes. 

Large 12mo, 
Johnson's (C. M.) Rapid Methods for the Chemical Analysis of Special 

Steels, Steel-Making Alloys and Graphite Large 12mo, 

Johnson's (J. B.) Materials of Construction 8vo, 

Keep's Cast Iron '. 8vo, 

Lanza's Applied Mechanics 8vo, 

Maire's Modern Pigments and their Vehicles 12mo, 

Martens's Handbook on Testing Materials. (Henning.) 8vo.- 

Maurer's Techincal Mechanics 8vo, 

Merriman's Mechanics of Materials 8vo, 

* Strength of Materials 12mo, 

Metcalf's Steel. A Manual for Steel-users 12mo, 

Sabin's Industrial and Artistic Technology of Paint and Varnish 8vo, 

Smith's ((A. W.) Materials of Machines 12mo, 

Smith's (H. E.) Strength of Material 12mo. 

Thurston's Materials of Engineering 3 vols., 8vo, 

Part I. Non-metallic Materials of Engineering 8vo, 

Part II. Iron and Steel 8vo, 

Part III. A Treatise on Brasses, Bronzes, and Other Alloys and their 

Constituents 8vo, 

Wood's (De V.) Elements of Analytical Mechanics 8vo, 

Treatise on the Resistance of Materials and an Appendix on the 

Preservation of Timber 8vo, 2 00 

Wood's (M. P.) Rustless Coatings: Corrosion and Electrolysis of Iron and 

Steel 8vo, 4 00 



STEAM-ENGINES AND BOILERS. 

Berry's Temperature-entropy Diagram 12mo, 2 00 

Carnot's Reflections on the Motive Power of Heat. (Thurston.) 12mo, 1 50 

Chase's Art of Pattern Making 12mo, 2 50 

Creighton's Steam-engine and other Heat Motors 8vo, 5 00 

Dawson's "Engineering" and Electric Traction Pocket-book. .. . 16mo, mor. 5 00 

Ford's Boiler Making for Boiler Makers > •. 18mo, 1 00 

* Gebhardt's Steam Power Plant Engineering 8vo, 6 00 

Goss's Locomotive Performance 8vo, 5 00 

Hemenway's Indicator Practice and Steam-engine Economy 12mo, 2 00 

Hutton's Heat and Heat-engines 8vo, 5 00 

Mechanical Engineering of Power Plants 8vo, 5 00 

Kent's Steam boiler Economy 8vo, 4 00 

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Kneass's Practice and Theory of the Injector 8vo, 

MacCord's Slide-valves 8vo, 

Meyer's Modern Locomotive Construction 4to, 

Moyer's Steam Turbine 8vo, 

Peabody's Manual of the Steam-engine Indicator 12mo, 

Tables of the Properties of Steam and Other Vapors and Temperature- 
Entropy Table 8vo. 

Thermodynamics of the Steam-engine and Other Heat-engines. . . .8vo. 

Valve-gears for Steam-engines 8vo. 

Peabody and Miller's Steam-boilers 8vo, 

Pupin's Thermodynamics of Reversible Cycles in Gases and Saturated Vapors. 

(Osterberg.) 12mo. 

Reagan's Locomotives: Simple, Compound, and Electric. New Edition. 

Large 12mo, 

Sinclair's Locomotive Engine Running and Management 12mo, 

Smart's Handbook of Engineering Laboratory Practice 12mo, 

Snow's Steam-boiler Practice 8vo, 

Spangler's Notes on Thermodynamics 12mo, 

Valve-gears 8vo, 

Spangler, Greene, and Marshall's Elements of Steam-engineering 8vo 

Thomas's Steam-turbines 8vo, 

Thurston's Handbook of Engine and Boiler Trials, and the Use of the Indi- 
cator and the Prony Brake . 8vo, 

Handy Tables 8vo, 

Manual of Steam-boilers, their Designs, Construction, and Operation 8vo, 

Manual of the Steam-engine 2vols.. 8vo. 

Part I. History, Structure, and Theory 8vo, 

Part II. Design, Construction, and Operation 8vo, 

Steam-boiler Explosions in Theory and in Practice 12mo, 

Wehrenfennig's Analysis and Softening of Boiler Feed-water. (Patterson). 

8vo, 

Weisbach's Heat, Steam, and Steam-engines. (Du Bois.) 8vo. 

Whitham's Steam-engine Design 8vo, 

Wood's Thermodynamics, Heat Motors, and Refrigerating Machines. . ,8vo, 



MECHANICS PURE AND APPLIED. 

Church's Mechanics of Engineering 8vo. 6 00 

Notes and Examples in Mechanics 8vo. 

Dana's Text-book of Elementary Mechanics for Colleges and Schools .12mo, 
Du Bois's Elementary Principles of Mechanics: 

Vol. I. Kinematics 8vo. 

Vol. II. Statics 8vo, 

Mechanics of Engineering. Vol. I Small 4to, 

Vol. II Small 4to, 

* Greene's Structural Mechanics 8vo, 

James's Kinematics of a Point and the Rational Mechanics of a Particle. 

Large 12mo, 

* Johnson's (W. W.) Theoretical Mechanics 12mo. 

Lanza's Applied Mechanics 8vo. 

* Martin's Text Book on Mechanics. Voi. I, Statics 12mo, 

* Vol. II, Kinematics and Kinetics. 12mo. 
Maurer's Technical Mechanics 8vo, 

* Merriman's Elements of Mechanics 12mo, 

Mechanics of Materials 8vo, 

* Michie's Elements of Analytical Mechanics 8vo, 

Robinson's Principles of Mechanism 8vo. 

Sanborn's Mechanics Problems Large 12mo, 

Schwamb and Merrill's Elements of Mechanism 8vo, 

Wood's Elements of Analytical Mechanics 8vo, 

Principles of Elementary Mechanics 12mo, 



SI 


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MEDICAL. 

* Abderhalden's Physiological Chemistry in Thirty Lectures. (Hall and 

Defren.) 8vo, 

von Behring's Suppression of Tuberculosis. (Bolduan.) 12mo, 

Bolduan's Immune Sera 12mo, 

Bordet's Studies in Immunity. (Gay). (In Press.) 8vo, 

Davenport's Statistical Methods with Special Reference to Biological Varia- 
tions 16mo, mor. 

Ehrlich's Collected Studies on Immunity. (Bolduan.) 8vo, 

* Fischer's Physiology of Alimentation Large 12mo, 

de Fursac's Manual of Psychiatry. (Rosanoff and Collins.).. . .Large 12mo, 

Hammarsten's Text-book on Physiological Chemistry. (Mandel.) 8vo, 

Jackson's Directions for Laboratory Work in Physiological Chemistry. .8vo, 

Lassar-Cohn's Practical Urinary Analysis. (Lorenz.) 12mo, 

Mandel's Hand-book for the Bio-Chemical Laboratory 12mo, 

* Pauli's Physical Chemistry in the Service of Medicine. (Fischer.) ..12mo, 

* Pozzi-Escot's Toxins and Venoms and their Antibodies. (Cohn.). . 12mo, 

Rostoski's Serum Diagnosis. (Bolduan.) 12mo, 

Ruddiman's Incompatibilities in Prescriptions 8vo, 

Whys in Pharmacy. 12mo, 

Salkowski's Physiological and Pathological Chemistry. (Orndorff.) .. ..8vo, 

* Satterlee's Outlines of Human Embryology 12mo, 

Smith's Lecture Notes on Chemistry for Dental Students 8vo, 

* Whipple's Tyhpoid Fever Large 12mo, 

Woodhull's Notes on Military Hygiene 16mo, 

* Personal Hygiene 12mo, 

Worcester and Atkinson's Small Hospitals Establishment and Maintenance, 
and Suggestions for Hospital Arcnitecture, with Plans for a Small 
Hospital 12mo, 1 25 



METALLURGY. 

Betts's Lead Refining by Electrolysis 8vo, 4 00 

Bolland's Encyclopedia of Founding and Dictionary of Foundry Terms used 

in the Practice of Moulding 12mo, 

Iron Founder 12mo, 

Supplement 12mo, 

Douglas's Untechnical Addresses on Technical Subjects 12mo, 

Goesel's Minerals and Metals: A Reference Book 16mo, mor. 

* Iles's Lead-smelting 12mo, 

Johnson's Rapid Methods for the Chemical Analysis of Special Steels, 

Steel-making Alloys and Graphite Large 12mo, 

Keep's Cast Iron 8vo, 

Le Chatelier's High-temperature Measurements. (Boudouard — Burgess.) 

12mo, 

Metcalf 's Steel. A Manual for Steel-users 12mo. 

Minet's Production of Aluminum and its Industrial Use. (Waldo.). . 12mo, 

Ruer's Elements of Metallography. (Mathewson) 8vo. 

Smith's Materials of Machines 12mo, 

Tate and Stone's Foundry Practice 12mo, 

Thurston's Materials of Engineering. In Three Parts 8vo, 8 00 

Part I. Non-metallic Materials of Engineering, see Civil Engineering, 
page 9. 

Part II. Iron and Steel 8vo, 3 50 

Part III. A Treatise on Brasses, Bronzes, and Other Alloys and their 

Constituents 8vo, 2 50 

Ulke's Modern Electrolytic Copper Refining 8vo, 3 00 

West's American Foundry Practice 12mo, 2 50 

Moulders' Text Book 12mo, 2 50 

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MINERALOGY. 



Baskerville's Chemical Elements. (In Preparation.). 

Boyd's Map of Southwest Virginia Pocket-book form. 

* Browning's Introduction to the Rarer Elements 8vo, 

Brush's Manual of Determinative Mineralogy. (Penfield.) 8vo, 

Butler's Pocket Hand-book of Minerals 16mo, mor. 

Chester's Catalogue of Minerals 8vo, paper, 

Cloth, 

* Crane's Gold and Silver 8vo, 

Dana's First Appendix to Dana's New "System of Mineralogy". .Large 8vo, 
Dana's Second Appendix to Dana's New "System of Mineralogy." 

Large 8vo, 

Manual of Mineralogy and Petrography 12mo, 

Minerals and How to Study Them 12mo, 

System of Mineralogy Large 8vo, half leather, 

Text-book of Mineralogy... 8vo, 

Douglas's Untechnical Addresses on Technical Subjects 12mo, 

Eakle's Mineral Tables 8vo, 

Eckel's Stone and Clay Products Used in Engineering. (In Preparation). 

Goesel's Minerals and Metals: A Reference Book 16mo, mor. 

Groth's Introduction to Chemical Crystallography (Marshall) 12mo, 

* Hayes's Handbook for Field Geologists 16mo, mor. 

Iddings's Igneous Rocks 8vo, 

Rock Minerals 8vo, 

Johannsen's Determination of Rock-forming Minerals in Thin Sections. 8vo, 

With Thumb Index 

* Martin's Laboratory Guide to Qualitative Analysis with the Blow- 

pipe 12mo, 

Merrill's Non-metallic Minerals: Their Occurrence and Uses 8vo, 

Stones for Building and Decoration 8vo, 

* Penfield's Notes on Determinative Mineralogy and Record of Mineral Tests. 

8vo, paper, 

Tables of Minerals, Including the Use of Minerals and Statistics of 

Domestic Production 8vo, 

* Pirsson's Rocks and Rock Minerals 12mo, 

* Richards's Synopsis of Mineral Characters 12mo, mor. 

* Ries's Clays: Their Occurrence, Properties and Uses 8vo, 

* Ries and Leighton's History of the Clay-working Industry of the United 

States 8vo, 

* Tillman's Text-book of Important Minerals and Rocks 8vo, 

Washington's Manual of the Chemical Analysis of Rocks. , ,,,,,, 8vo, 



MINING. 

* Beard's Mine Gases and Explosions Large 12mo, 3 00 

Boyd's Map of Southwest Virginia Pocket-book form, 2 00 

* Crane's Gold and Silver 8vo, 5 00 

* Index of Mining Engineering Literature 8vo, 4 00 

* 8vo, mor. 5 00 

Douglas's Untechnical Addresses on Technical Subjects 12mo, 1 00 

Eissler's Modern High Explosives 8vo, 4 00 

Goesel's Minerals and Metals: A Reference Book , 16mo, mor. 3 00 

Ihlseng's Manual of Mining 8vo, 5 00 

* Iles's Lead Smelting 12mo, 2 50 

Peele's Compressed Air Plant for Mines 8vo, 3 00 

Riemer's Shaft Sinking Under Difficult Conditions. (Corning and Peele).8vo, 3 00 

* Weaver's Military Explosives 8vo, 3 00 

Wilson's Hydraulic and Placer Mining. 2d edition, rewritten 12mo, 2 50 

Treatise on Practical and Theoretical Mine Ventilation 12mo, 1 25 

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SANITARY SCIENCE. 

Association of State and National Food and Dairy Departments, Hartford 

Meeting, 1906 8vo, $3 00 

Jamestown Meeting, 1907 8vo, 

* Bashore's Outlines of Practical Sanitation 12mo, 

Sanitation of a Country House 12mo, 

Sanitation of Recreation Camps and Parks 12mo, 

Folwell's Sewerage. (Designing, Construction, and Maintenance.) 8vo, 

Water-supply Engineering „ 8vo, 

Fowler's Sewage Works Analyses 12mo, 

Fuertes's Water-filtration Works 12mo, 

Water and Public Health 12mo, 

Gerhard's Guide to Sanitary Inspections 12mo, 

* Modern Baths and Bath Houses 8vo, 

Sanitation of Public Buildings 12mo, 

Hazen's Clean Water and How to Get It Large 12mo, 

Filtration of Public Water-supplies 8vo, 

Kinnicut, Winslow and Pratt's Purification of Sewage. (In Preparation.) 
Leach's Inspection and Analysis of Food with Special Reference to State 

Control 8vo, 

Mason's Examination of Water. (Chemical and Bacteriological) 12mo, 

Water-supply. (Considered principally from a Sanitary Standpoint). 

8vo, 

* Merriman's Elements of Sanitary Engineering 8vo, 

Ogden's Sewer Construction 8vo, 

Sewer Design 12mo, 

Parsons's Disposal of Municipal Refuse 8vo, 

Prescott and Winslow's Elements of Water Bacteriology, with Special Refer- 
ence to Sanitary Water Analysis 12mo, 

* Price's Handbook on Sanitation 12mo, 

Richards's Cost of Cleanness 12mo, 

Cost of Food. A Study in Dietaries 12mo, 

Cost of Living as Modified by Sanitary Science 12mo, 

Cost of Shelter 12mo, 

* Richards and Williams's Dietary Computer 8vo, 

Richards and Woodman's Air, Water, and Food from a Sanitary Stand- 
point 8vo, 2 00 

* Richey's Plumbers', Steam-fitters', and Tinners' Edition (Building 

Mechanics' Ready. Reference Series) 16mo, mor. 1 50 

Rideal's Disinfection and the Preservation of Food 8vo, 4 00 

Sewage and Bacterial Purification of Sewage. 8vo, 4 00 

Soper's Air and Ventilation of Subways 12mo, 2 50 

Turneaure and Russell's Public Water-supplies 8vo, 5 00 

Venable's Garbage Crematories in America 8vo, 2 00 

Method and Devices for Bacterial Treatment of Sewage 8vo, 3 00 

Ward and Whipple's Freshwater Biology. (In Press.) 

Whipple's Microscopy of Drinking-water 8vo, 3 50 

* Typhoid Fever Large 12mo, 3 00 

Value of Pure Water Large 12mo, 1 00 

Winslow's Systematic Relationship of the Coccaceae Large 12mo, 2 50 



MISCELLANEOUS. 

Emmons's Geological Guide-book of the Rocky Mountain Excursion of the 

International Congress of Geologists Large 8vo. 1 50 

Ferrel's Popular Treatise on the Winds 8vo, 4 00 

Fitzgerald's Boston Machinist 18mo, 1 00 

Gannett's Statistical Abstract of the World 24mo, 75 

Haines's American Railway Management 12rrio, 2 50 

Hanausek's The Microscopy of Technical Products. (Winton).. . . . . .8vo, 5 00 

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Jacobs's Betterment Briefs. A Collection of Published Papers on Or- 
ganized Industrial Efficiency 8vo, $3 50 

Metcalfe's Cost of Manufactures, and the Administration of Workshops. .8vo, 5 00 

Putnam's Nautical Charts 8vo, 2 00 

Ricketts's History of Rensselaer Polytechnic Institute 1824-1894. 

Large 12mo, 3 00 

Rotherham's Emphasised New Testament Large 8vo, 2 00 

Rust's Ex-Meridian Altitude, Azimuth and Star-finding Tables 8vo, 5 00 

Standage's Decoration of Wood, Glass, Metal, etc 12mo, 2 00 

Thome's Structural and Physiological Botany. (Bennett) 16mo, 2 25 

Westermaier's Compendium of General Botany. (Schneider) 8vo, 2 00 

Winslow's Elements of Applied Microscopy 12mo, 1 50 



HEBREW AND CHALDEE TEXT-B000KS. 

Gesenius's Hebrew and Chafdee Lexicon to the Old Testament Scriptures. 

(Tregelles.) Small 4to, half mor, 5 00 

Green's Elementary Hebrew Grammar 12mo, 1 25 



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